If I recall correctly, 9.1E was still clinging to life in the 11.0 days. So, especially given its still-strong install base, we may not see 10.2B08 retire right when 12.0 ships. That's just my guess, I don't have any inside info on that. But I have heard that they're actively planning 12.x features now.
But certainly 10.2B is living on borrowed time. No one should plan to upgrade to it at this point, and anyone on it should have a solid plan to upgrade from it soon.