So considering that Nintendo is aware of how talented David Wise is and that they even asked him to score for both the first and second DKCR games, how likely is it that you think he'll be working on the new Metroid soundtrack???

I think it's very likely and there were times throughout the DKCTF that I felt like the music, and art style too, was a perfect fit for a 2d metroid game; the Jungle world in particular (World 5 or 6 was it?).  I mean does anyone now if Mr. Wise is freelance or on contract?  Because you don't want to let a guy like that go and hes clearly gotten on the radar again now with Tengami and DK.

From what I know he hasn't been so active lately, but what's Tengami?

I doubt he would be the one working on metroid. Kenji Yamamoto has been working for retro studios since metroid prime. And David Wise has his own music studio.

Whoever did the soundtracks before was brilliant enough that they don't have to bother with changing it.

Kenji Yamamoto did, and he works with Retro permanently from what i can tell. 

What metroid?

IF they happen to be working on a new Metroid, Wise will not be the primary contributor for the soundtrack. Yamamoto would have that covered, probably. I mean, maybe I could see Wise as a guest with a track or two at most if he just likes working with Retro and perhaps that's just fanciful.

If their project is not Metroid, I could indeed see Wise taking a big role on the soundtrack. Having asked him back for DKCR I think they'd like to keep his talent employed, if reasonably affordable.

You're making a very large assumption there in the OP...

While hiring David was a pretty Wise decision, I still think Yamamoto should continue composing the music for future Metroid games!

I hope not. Yamamoto is the best possible composer for the job.