Definitely sooner than I expected...but I'm not that surprised. Can't say that I have seen a ton of his play, but from what I have seen, he is an athletic kid that has great hands and footwork, an outside stroke at least on par with Dalembert, more tools in his low-post offensive game than Sammy, and has a big enough body that he can defend in the low-post reasonably well (that weak-side block on David Lee was pretty impressive). While it is likely that - at least initially - Sammy is still probably the better low-post defender, I think that Speights will eventually mesh MUCH better with Brand (especially on the offensive end) than Sammy will.
I just figured that it was summer league/preseason flashing, but I trust the coaching staff to know if it is for real or not.
I would still think that Sammy will be the starter on Opening Night (ex injuries), but he should be on notice: time to tighten up your game, son...