Well, you could consider the $50 as paying the annual fee off, then you'd basically get twice as many DD as usual with the 2% vs your usual 1% for the whole next year. Then you could downgrade again! So thats not too bad.
But it might be better to open a new Disney Premier card, since you'd get 100DD to start off with instead of 50.
I got the initial offer to upgrade back around Christmas but I don't remember if there was any bonus attached at that point. I saw the words "annual fee" and it hit the trash. It was a fancy large booklet about 10" x 5" that must've cost a mint to print and mail. I received the same thing just a couple days ago but it did offer the 5% for the first 3 months on the last page of the booklet. This time I did upgrade, got some pixie dust

when a Chase rep gave me credit for a
Disney cruise that I had booked a few weeks before I got the offer (I asked for it, was denied initally, then got it the second call back

) and am good to go this summer with 5% on Disney purchases, gas, grocery and dining...gonna make my life (and my husband's -- he HATES having to think about what card to use, when!) so much easier this summer...no trading off between Chase Freedom, Discover and other cards to score the max % per transaction! Whew!!
Good luck to you, maybe the offer will show up soon!