As noted above, release 36 (which is on all developer devices now, and production devices that have opted in), has secure storage available to squirrel.
With this, you can securely hold multiple sets of credentials on a device (separate from the code) and use code to switch between them, scan networks & pick the best one, alternate settings based on time, etc.
However, this happening automatically is not part of the OS at this point. Different customers have different requirements for multi network support so we have not built this in. A simplistic multi-network setup has been on our roadmap for a while, but in the meantime it turned out that this wouldn't really satisfy anything beyond the most simple use cases.
It'll still happen at some point, but no fixed release schedule right now.