[Someone1234]

Yes, however that is just getting Google App features earlier. So if a product isn't in the GApps pipeline you won't get it, opt in or not.

[Navarr]

Inbox has declared since day 1 they plan to come to GApps. No idea what the hold up is. They dodged my question asking about the challenges during the AMA. (I think they chose not to answer it at all)