^ What he said. Since the show is produced by Disney in the first place, moving it to ABC wasn't exactly tough. The only reason it hasn't been officially announced is because they couldn't announce it until the contract with NBC expired, which it just did with the airing of this episode.
Really, it should have been obvious that wasn't the finale. For one, why was Kelso still Chief of Medicine, when he had quit two episodes before? Why did Keith magically reappear after being missing for so long? Clearly this was an episode aired out of order, likely because NBC wanted something special for the finale, and the whole story-based thing fits that.
The whole reason why the show is getting another season is because NBC refused to finance anymore episodes, and Bill Lawrence refused to alter an episode to serve as the series finale, wanting to give a proper send-off for the show. ABC offered to pick it up, and here we are. It'll also likely be starting in the fall, as far as I've heard, which hasn't been the norm for the past two or three seasons.
Anywho, it would have been a bad finale (what with the out-of-orderness), but as an episode I actually quite liked it. It had the humour of the old episodes, the over-the-topness of the new episodes, and even tossed a little drama in there at the end. Jan Stevens had a brilliant moment (I believe he's still the composer) at the end where Dr. Cox said the "Let's just say that's how I'm telling it..." line and he went to a minor note to denote just a hint of sadness. Solid composing.
Here's a nice 'Welcome to Season 8' video from the cast and crew.