Not yet. I believe that the Disney Files magazine stats maybe in the fall. Any reservations book prior to that date that have the dining plan already added, will still be able to pay at check in.
Just added the dining plan yesterday for our trip in 10 days and MS said for us to pay at check in. We're also doing a split stay...2 nights in a studio and 4nights in a 1 bdrm, and MS said we would have to pay separately for the different room stays. However, they 'linked' it just in case our waitlist came through for those last 2 nights in the 1 bdrm so the dining plan would be linked also.
Nope - per MS, they aren't even set up to accept prepayment right now even if you wanted to. Just add the DDP to your reservation at least 48 hours in advance of your trip and pay at check-in.