Looking through the "Google's Blogs" section I found a Youtube developers blog post that reads

<<Last Thursday at the Google Developer Day, we announced that the next iteration of the API will be based on the Google data ("GData") standard! We hope to release read feeds later this summer.>>

They have a presentation on it at http://youtube.com/watch?v=OqmHjuD_a1M

Further down the subheading "Why GData?" appears which reads

>- Better scalability/stability/flexibility
>- Standardizing on an existing framework – easier to mash up with >other GData APIs
>- Setting us up for write feeds later in the year by using the >authentication models
>- Developers can leverage GData resources, such as client libraries >and developer guides

They then explain what will happen to the old API

<<The existing API will continue to be available for the foreseeable future, but all new features will be built into the GData API. Plenty of notice will be given before the current API goes anywhere.>>