[DISCUSS] 5.1 should be 6.0

[Jon Haddad]

Keeping this short.  I'm not sure why we're calling the next release 5.1.
TCM and Accord are a massive thing.  Other .1 / .2 releases were the .0
with some smaller things added.  Imo this is a huge step forward, as big as
5.0 was, so we should call it 6.0.