It's tricky - having a separate blog might be a good idea once the Pyra is out and available, and the PandoraLive blog can concentrate on those of us who've decided not to get a Pyra and stick with the Pandora, but hopefully (and signs show that) the number of those people will be low. More likely the Pandora blog will be used by people who intend to upgrade in the future when funds allow, so would also continue to be interested in the Pyra.
I think having one blog with categories you could filter on will be best. Now as for the name, I'd suggest that PandoraLive is a known brand that can be built on, so unless a much better name can be found and registered I'd stick with that even after the Pandora becomes mostly irrelevant.