I've gone ahead and built a very provisional, alpha version of 2015.2.0.0 using GHC 7.10 RC3.

I bumped all the GHC libs to the versions in 7.10, and bumped all the Platform libs to the latest versions I could find on Hackage. There were a few issues:

old-locale and old-time - no longer part of GHC, but cabal-install, cgi & HTTP need them - and they are part of the platform - so included now as added packages. Not sure this is a great idea, since they are now very deprecated... but until cabal-install, cgi, & HTTP update, not sure what else to do.
tf-random - is now required by alex and QuickCheck - seems a shame to add this, as now we're going to have two random packages
network-uri - was split out of network, and needed by cabal-install, cgi, & HTTP. I suppose we should include it, as it was functionality and API that was part of the platform
exceptions & multipart - needed by cgi - is exceptions now subsumed by something in transformers? and... multipart? maybe time to drop cgi? We didn't have it last time anyway as it wouldn't compile!
scientific - needed by attoparsec - debated in detail last time ... and we're still here!

The Platform is significantly larger now: On OS X it has gone from 316M to 499M! Most of this is due to new OpenGL libs which are now huge (went from 98M to 239M!) GHC itself grew by 109M (to almost 1G), so that the whole installed magilla is 1.5G! Even the compressed installer is now 250M!

If you want to poke at it, the source is in the pre-release branch at GitHub, and the OS X builds are at my usual platform staging area:

Index of /mark/platform

Remember, it already includes GHC, so no need to download the GHC binary for OS X that is there, too.

I'll try to get a generic linux build up soonish... but my VM now runs out of memory trying to build OpenGL - and adding more only makes my machine thrash to death!

- Mark