I think we've already seen what Fournier and Kemba can do for the team. The Knicks over the pre-season have played with a pace and fluidity on offense rarely seen last year. Fournier, more so than anything else, is a playmaker. Fast decisions, makes the defense react and commit, creates movement. Kemba is more of the same. And both of these guys can hit the perimeter shot.
Fournier/Walker, having earned their big contracts, don't need to be greedy to prove themselves for the next big contract. All of these pros have egos, but given that they came to the Knicks to be part of a winning team and NOT to be the superstars, they can focus on the goal of making their teammates and the team overall look good.
RJ looks ready to take another step forward and he'll need to continue to get more opportunities to continue his development. Fournier is good enough as a veteran to hold his own vs RJ and rightly demand his own touches. But I think he understands that he's here to support RJ's ascent... and if RJ isn't ready, step in and take over when needed from the wing.