Sounds like an opportunity for some of the other backend providers to create a migration guide and import tools!
Edit: It occurs to me that this is slightly complicated by the need to have API compatibility with StackMob, and I don't know the space well enough to know if anyone does that. In other PaaS businesses I'm aware that some companies maintain drop-in replacements for the market leader, because they make it possible to poach clients without asking for a $X00,000 rewrite.