1. I don’t know, I think so. No news about scaling it back.
2. I know that some Interrailers in Sweden were part of it. Basically the far edges of Europe and some central European countries that are difficult to circumnavigate.
3. One travel day extra.
4. In-/outbound days enable you to travel in your home country. Wether you use it to exit the country, travel through it, or travel in it is all possible. See it as a “home country day”. What you do with it, is your choice.

There have been reports for sure from Sweden (4 days sometimes), the Netherlands and Switzerland.

I understood that if you were in the pilot countries you would simply see a higher number in your available In/Out days. That was with a mobile pass.

I lost interest when, not surprisingly, the UK was not included. You can just about get to London and beyond in a day from most, if not all, of the UK.

I doubt there’s many parts of the continent where you can’t reach a border in a single day - even if it’s a long and inconvenient journey - but the far north of Scotland would probably do it. Possibly some parts of Scandinavia.

I’d happily pay more for a UK pass that came with extra inbound / outbound days. I certainly get a lot of value from them travelling down from Newcastle in the morning peak.

I think I read somewhere another scenario was residents of countries such as Germany were being penalised if they wanted to cross the country e.g. Brussels to Copenhagen. So I think there may be a case for piloting an extra day to assess whether it would be used in that way, not a free day to jolly around your COR. 

Edit - a better example is Verona to Munich passing through Austria and Switzerland. An Austrian would lose a COR.

It may also be worth considering the option to purchase an extra Cross - COR day onto your pass. Obviously no value to the UK user.

On the other end of the scale there are those of us for whom they are completely useless, perhaps there should be a discount for having zero in/out days, it would make it feel less like we are cross-subsidising those in certain other countries getting extra perks.

For trips with normal trains, tickets from/to the border are not so difficult to be bought, (from the Netherlands/Belgium to Germany, you can buy them online with 100% reduction for the Dutch, Belgian, or German resident-part, so you only pay for the part without using an Inbound/Outbond trip) for the other countries. It's not able for who uses a global-priced-train, for then would extra inbound/outbound days very usefull. I won't have no problem when for extra days 10-15 Euro would be payable. It's important that Interrail will come with a solution for ALL European residents.

and for people who not live in UK who must go back home extra (work, wedding, funeral), extra inbound-outbound would be extra helpful, because Eurostar doesn't sell tickets from/to the border, or supplements which covers the residental part of the trip. They have to buy a normal-ticket (and can lost a travel day if they have to use a connected train from/to Londen, Brussels, Rotterdam or Amsterdam!).

I have to respectfully disagree with you. 
Firstly the In/Out or COR days (Country of residence) are not extra days in your pass so you pay for X days irrespective of which country you travel in. As such nobody is getting more financial benefit from these In/Out days than us, simply the ability to include your home providers on those days as well as all the other countries. We are certainly not subsidising anybody else as we still get X days unlimited transport, whether we use these days or not. I have done a few adventures now where I used a flight to start or end my adventure and then had an extra day in mainland Europe. I do not regret not using my COR day - Or I could have used both days to facilitate a stay in London.

One of the countries that gets the best “cash” or “value” deal from COR days is without doubt the UK, as you well know if you live in the North East. For an early train to London you could easily pay £100+ (£200+ if you have a first class pass) and Eurostar can easily cost the same again at peak times.

As you rightly state it is only the extremes of the UK that would have to need to leave very early to get to London in time for a late Eurostar.

I was also very careful to avoid the suggestion that any pass users would use these COR days in any way not the spirit of their intended use - i.e. to facilitate adventures in other countries. 

Well, this might be a typical case of lack of empathy and superficial-thinking (if i may express it so directly!). It wouldn't be difficult to understand that travellers with a 1-2-3 month-pass must go back to home for more times. Many employers wouldn't give his employees leave over a continuous period of 2-3 months and there would occur cases like funeral, wedding of there might be another reason for coming-back to home for interrupt the holiday. For these group there should come a solution (and it won't be a problem if Interrail would account modest-cost for this. It would be better if some people would think further than his/her own wishes and needs, thank you.

The rules are clear - this allowance is for 2 days (3 in pilot) irrespective of duration of the pass. In the case of extraordinary circumstances Interrail has a discretion and we often see posts where they have added back travel days.
But the In/Out days is relatively new but was always limited to avoid pass users effectively using it as a local travel pass. With a 4 day pass you could almost pay for it in one return journey from Edinburgh to London on a peak train with flexibility. 

We are all aware that we need to have contingency in our plans, just the same as if on a package holiday. 

I assure you there is nothing superficial or lack of empathy in my comments. If Interrail changes its IN/Out allowance I would be delighted, but in the meantime I will continue to make the maximum use of my Global passes.

OOI I have experienced the exceptional circumstances of a family illness and Interrail were amazing in their support. (It was not involving In/Out days)

In the Belgian railways’ information, I find this:

"So far, it has been agreed with SJ, ENTUR, TCDD, NMBS and SBB to give travellers from Sweden, Norway and Turkey four tokens and Swiss and Belgian travellers three tokens.”

(Under "Extra token(s) voor reizen in Country Of Residence (CoR)”)

Clearly, this is not complete, since people from the Netherlands also seem to get 3 inbound/outbounds. But it does give an idea of the countries involved and it looks like the (main?) operators in those countries have to agree. I suppose RDG don't want it (yet?).