Nope they made it widescreen about a week ago.

"As we pointed out last week, YouTube is now offering HD quality video on select movies. But one of the hallmarks of HD video is the widescreen aspect ratio (16:9 rather than 4:3) and now the YouTube site has been updated so that all video is now displayed in a new widescreen player. As the YouTube blog notes, this means that the vast majority of videos on the site — which were uploaded as 4:3 — are now displayed with black bars on the sides (the empty space not used by 4:3 videos).
You might be wondering why YouTube doesn’t auto-detect a video’s aspect ration and use the appropriate player — it’s a good question, one that many YouTube users are also asking, but so far the company hasn’t commented. We suspect the change is part of a broader move to make YouTube all HD, all the time, but it seems like giving video owners the option to choose which player is used would have been a sound idea."