Yeah shame he's not playable, but it's no bother. The final product is what counts anyway. And as far as I see, no fundamental moveset changes outside maybe getting a 'gentleman' in our AAA combo, which is great. Rather have no tail moves than that waggle attack anyway.
DTilt has always been great yeah and I don't expect nerfs to it, neither to F Air, B Air or D Air. I actually sort of hope N Air and U Air get buffed. At least more priority and damage on N Air (a move which is greatly underused anyway). And U Air also needs to have more damage, as just 6% just doesn't cut it, and it's just about THE MOST nerfed move in Smash 4 patch history.
I also hope Dash Attack becomes as useful as in Brawl yet again, but by the looks of it, it'll work like it did in Smash 4. At least am hoping for it to speed up, have a little more range and less lag. Diddy's cartwheel was always superior to DK's roll, so kinda hoping to see that still in Ultimate. Kinda hope his recovery also won't be as bad as in Smash 4.
But as far as I've seen, most Top Tiers remain Top Tier. Mario, Fox, Bayonetta, Cloud, Mewtwo, Marth, Sheik.. all seem to remain very solid characters. I have no reason to expect huge nerfs from Diddy. Especially since he was already adressed in Smash 4, and the most complaints in the last year and a half or so where from characters as Sheik, Cloud and Bayonetta. To me it seems Diddy should be relatively safe.
Neutral is gonna be fun, but the whole focus on a more offensive neutral game would actually benefit Diddy I expect. We're gonna need to change up our approach slightly, less waiting, more taking chances.