Well, I don't know if he's enough for KG to consider staying in Minnesota, but he's enough for Minnesota to hold off on trading away KG. I'll explain that.
If KG wanted to contend for a title immediately, I would have to think he'd be best off demanding a trade and not believing that Foye is going to be a star right away. However, from Minny's point of view, a Foye and KG tandem surrounded with solid roleplayers is their best shot at winning a title in the forseeable future. It's not likely that they'll win a title, but it's the Wolves' best shot.
I'd like to add that the Foye hype is getting out of hand (not in this thread in particular, just in general). Maybe hype is the wrong word. Expectations is perhaps more accurate. The way certain guys compared him to Wade (Jay F'in Bilas, for instance) before the draft is ridiculous. No one can expect for their pick to turn into a Wade caliber player, and certainly one can't expect that to happen right away. I think Foye will be a very good and maybe even great player, but it's unfair to expect him to be the franchise savior right away.