Think Google App Engine with more languages, with real database access (bring your own db if you want, or they can host it), dozens of add-ins, and a sane pricing model.
by sane you mean really expensive for hobby projects. I keep thinking this will be a problem in the long run, disruptive technologies tend to be bottom up. I can't host a message board on heroku because it's way too expensive.
The sweet spot is having very reasonable billing like $15/month for a 20GB database (5MB free) and $35/month for a 2 dedicated workers (or free for 1 which needs to be spun up and is ~10 seconds for the first request). My current use case is projects which could become small income earners, where ~50/month to experiment is dirt cheap if it saves me hours of setup time.
I wish there were something between the $15 and $200 db offerings.