The point of such an early dev kit isn't to commit in advance but get people to try out what works, then select what will be in the final product (and maybe releasing updated dev kits on the way). They're would be a general plan, but this isn't like a game console dev kit where almost all specs and major features are set in advance, so you'd expect devs to implement multiple variants of each software feature and see what they require of the hardware, how people use it, how popular they are, etc.