Oh, absolutely. Hey, I love 8-Bit MM as much as the next classic fan, and I'd have NO issue with MM10 or MM11 being done in 8-Bit at all. However, a Wario Land: Shake It MM game would truly look incredible, and I'd be all for it.
If it's going to be something new graphically, I say, use that for either a) the X/Zero/ZX series or b) a new series that continues in the same vein (being an action-platfomer).
Personally, Rockman 9 just reminded me a whole bunch of why I came to love this series in the first place, and I would prefer to keep it that way. So, as far as I'm concerned, let Rock stay with being 8-bit, and they can go ahead and "experiment" with the other series in this way, if they so wished.
I mean, the X series was one that first dared to push Rockman beyond his 8-bit boundaries. Let it continue to do so. It's what it was constructed around, and it would fit.