Doing a quick survey of what the major platforms offer, I found
EL 6.6: CMake 2.8.12
Ubuntu 14.04 LTS: CMake 2.8.7
Debian 7.0: CMake 2.8.9
FreeBSD 9.3: CMake 2.8.12
Bumping up to requiring 2.8 would allow use of generator expressions. I’d be able to use that to properly fix the CMake policy warnings in bro-aux about using the LOCATION target property.
Bumping up to 2.8.8 would allow use of OBJECT libraries. That would be a nice-to-have that I think would simplify CMake logic regarding how shared and static versions of libraries get built (e.g. would simplify broccoli, broker, and plugin support).
Not aware of anything in versions beyond 2.8.8 that make them compelling enough to consider.
It seems reasonable to now require 2.8.0, so I want to at least do that. And if Ubuntu 14.04 gets 2.8.8 before the next Bro release, I say switch to requiring 2.8.8. Other thoughts/opinions?