I haven't played either of the latest two 2D DKC games. I loved the first two DKC games for SNES (haven't played DKC3 yet). If find those games a lot of fun, with a good challenge, and lots of secrets.
The series lost me with DK64, one of the worst games I've ever played (and still own, by the way).
I need to play TF because I've only heard amazing things about it.
In the end, though, I hope Retro are working on something else. I wouldn't mind a new DKC game, but if it's between that and say, a Metroid game, I'd rather Metroid. Or a new IP.