The good news is that there are no major name changes or new attributes, this is a mandate to use already existing Item Specifics.
Throughout 2019, eBay have emphasised the importance of item specifics and how they increase the visibility of your listings on both eBay and on external search engines. The more data you give eBay about what you're selling, the better they can match your item to what a buyer is looking for. This is either through query search (which as well as titles makes use of Item specifics), left hand navigation filters and on category merchandising pages.
"Buyers' in home & garden and fashion categories are 65% more likely to use filters to narrow down their search results so they can more easily find what they're looking for."
With this in mind, eBay are giving you at least 8 weeks notice for you to prepare accordingly. These Item specifics values are available now in eBay listing flows and eBay encourage you to add them ahead of the deadline on the 31st of March.
You'll be forced to add them for new listings or when you revise existing listings in the future. Although Good til Cancelled listings will continue to renew if you don't add the new mandatory eBay item specifics requirements, when you go to add new stock in the future you'll be unable to do so until you add the Item Specifics so we would recommend you get this task done and out of the way as soon as possible, preferably before the end of March. The alternative course of action is of course to do nothing and just deal with each listing as and when you're forced to.