I'm in waiting mode, too. For me it's super important to work on something else, get my mind off all the nail-biting. It's still tough, though, either way.
I usually get my next "good" idea while I'm about half way through an ms. And there's a spark, something that calls out to me--usually a character. And while I finish the ms I'm working on, I also take time to character journal and free-write on the next potential project. Then by the time I complete the other ms I can be excited about a new idea, and start seriously on that while waiting for notes from critique partners on the last draft of my other project. Kinda this back and forth thing.
Except I'm totally distracted by this novella I'm working on right now and not working on my new ms like a good girl. :S