A lot of rumors have it earlier than that,
I would be skeptical of that, since GW doesn't release new warhammer army books/codexes during summer months or December.
They didn't used to release an armybook/codex
every single month, either, but they have lately. With the new schedule nothing seems especially sacred about the summer hiatus.
Space Marines are going to be released cuz they're The Codex, so it has to happen. Orks are doing fine competitively, but they're starting to get old to the point where really only certain very specific builds work anymore. (which I suppose is true of tyranids, and at least for the remainder of the week as a mono-build, Tau)
The only army I think that desperately needs love is Black Templar, and the rumor is GW just isn't sure what to do with them. (seems easy to me, honestly, price them like CSM, but with ATSKnF, which makes them clearly better, but they'll have less magical/fancy tech toys like the other MEQs to make up for it)
