From otehr discussions it would seem that there will probably be a 3 or 4 month wait before anything is released. It's fairly common for there to be nothing forthcoming from Adobe, then suddenly ... pop ... there it is.
It seems LR5 isn't all that stable yet anyway, so it's probably as well to stick with LR4's SDK, and make the tweeks when/if 5sdk is released.
I'm not sure if there was a question in there somewhere, or just ruminations..., but yes: in general it's best to stick with released/supported features. On the other hand, there is something to be said for knowing what's coming and planning for it, and maybe even using undocumented features in some cases, thus this thread: