Actually, Anagram, it's not that someone on the team had good sense. This no doubt has been in the planning stages for a long time and this would have been decided way before they announced it. The LA Times even said this idea was concieved two years ago;
In fact, Lasseter's original report in no way mentioned this would only be about Woody and Buzz, it only seemed that way since it was just an announcement with very minimal information;
Today's report revealed;
Where it's implied that the only relevance it has to Toy Story 3 is that it takes place soon after that film in the timeline.
We'll see how things go, if Buzz and Woody have a big part or if it's a brand new set of toys for a new audience, but I have, and have had since the original announcement, faith that this project will be of excellent standard. I don't view sequels as a bad thing, even if they end "perfectly". It's like what Lasseter said;