The version they get is based on the license agreement they have with Adobe. Since RIM is responsible for the port (with assistance from Adobe), RIM only has access to a particular version. This may not be the latest version. I would be happy with any version that supports stage3D. Hopefully, BB10 will be a great success and Adobe would then hopefully supply greater assistance to get it faster and possible support the latest version of AIR. It is a very complex situation.
From the JAM Europe Road map session: They have 3.3 AIR and just recently got 3.4 AIR to migrate to BB10. It will *not* be a part of the 10.1 release (QWERTY version), but more likely the 10.2 release.
No road map currently to bring BB10 to PlayBook. Not that it wont, it is not on the next few months roadmap since it is all about BB10 and form factor for Q10 devices. At one time, we speculated that we would get BB10 for PlayBook this summer, that does not look to be the case now.
It is also unlikely that we would get the current runtime of AIR in 10.2+, but probably just 3.4 (contract and licensing agreements). The roadmap is still evolving, so this could change.