GHC 8 will take some time. The current position is to prioritize those new extensions which start creeping up in Hackage libraries. There were significant changes to the codebase in 8 and I want to wait until it's stabilized. Eventually, yes.
I thought most extensions "just provide sugar" and are gone by the STG stage.. guess not =)
No, you're right. I just don't want to swap out the frontends right now (again, stability). I'll definitely be cherry picking bug fixes and non-pervasive changes once I get a solid test/benchmark suite setup.