Tim: Audio Hijack Pro 2 supports that currently - download it and try it out. You need to find the "GoogleTalkPlugin" process itself, by

1) Installing the Instant On extra

and

2) Option-clicking the source selector in the Input tab.

So, Audio Hijack Pro definitely can get Hangouts audio today, and the update will as well.

Kevin: No, I'm afraid not. We're very confident that current users will be able to use the update with little trouble.