I've now made vNext the default branch on GitHub - https://github.com/slodge/MvvmCross/
This means the portable library code is now the default view.
I do anticipate that this may cause some problems, especially while the MonoDevelop/Monotouch tooling is still a little behind the curve. If anyone needs the original version, then the old non-portable version is stil there and is still labelled master - https://github.com/slodge/MvvmCross/tree/master
However, I hope that most of you will be able to join me in developing portable code :)
The future is portable - and I'm really glad to be switching over to vNext - it's much cleaner and even more powerful than the first generation of MvvmCross.