Well, of course not NOW, it's too soon. But do you honestly believe that whenever Smash4 rolls around, years from now, that even if Sakurai maintains close ties with Nintendo he won't be involved? He was already a freelancer when Brawl was announced, for crying out loud. Iwata just wanted him on board that damn badly (lazy development threats).
Tell me you don't see the same thing happening if Sakurai is still under Nintendo's wing whenever they decide that they want to make a Smash4.
Well, let's put it this way:
Sakurai officially left HAL in 2003. Did that stop HAL and Ninty from putting out more Kirby games, without him on board? Certainly not. Hell, even some of the Kirby games that were crafted while he was STILL at HAL did not have his input at all (Kirby 64, KDL2 and KDL3 being among them).
So, I'm thinking that, with the position that Sakurai has now, it's not like he has that much more of a mandate to work on another Smash game, whenever that time may come, any more than he has one to work on another Kirby game. For all we know, he may not even be that interested in doing sequels. After all, if he was willing to let others do whatever the hell they wanted with Kirby, I'm sure Smash could follow suit, be it for good or ill.
Sakurai is well on the right track to being prepped up as the "New Miyamoto for a New Era!" that Ninty has probably needed for quite a while (I love Miyamoto as much the next N-fan, but really, we need a new flavor in the Kool-aid mix). This new deal, which just gives him more power, is only testament to what is probably inevitable. In that same light, if he's going to be just that, he may be able to afford to say "I don't necessarily want to be a part of this project [new Smash], but I give my blessing to all those involved! I'm just too busy with my own stuff!
"
If that ends up being what happens, I would not be at all surprised. If Sakurai is at all serious about how he wants to focus on new IPs, that would do more to entail that he can't afford to "look back" to the likes of Kirby and Smash. Let others handle that.