Nobody knows when there will be a discount. It is highly unlikely that there will be one until this summer though.

You can always wait to find out, it's not a problem to buy a pass the day before you leave

Special offers are not announced in advance. Going by the past few years, there were available in March, around Black Friday and in December/early January. Subscribe to the Eurail newsletter to be informed when one starts.

Thank you for your reply.   The problem I have is  booking seat reservations. Do I need a pass before I can reserve seats on trains. 

For most trains you don't. Check this thread for the best ways to book:

And also this page:
https://www.seat61.com/interrail-and-eurail-reservations.htm

If you have any questions about booking a train, then mention route, date and departure time.