God, I hope they don't do some other Xenos full army before they release the Orks. And I am really hoping that the wait on Orks is because they are finally planning on replacing some of the ancient Gorkamorka-2nd edition era kits and the resin models that they have. Just drop a new buggy/trakk kit, Ghazgkull & Badrukk, plastic Kommandos & tankbustas dual kit, and finally sell a real kit for the Deff Koptas and it would make me a happy 40k player.
Barring that - maybe finally modernize the Chaos Space Marines range with nice models? I am sick and tired of seeing constant new ****** when so much stuff is old and meh. I like new stuff as much as the next guy but I absolutely loathe GWs long-time policy to ignore massive swathes of their game and spend attention on a small section. The argument is that they concentrate on the stuff that sells best - but that argument is really circular since you can legitimately say that the popularity of some things is the fact that GW puts so much emphasis and attention into it. Stormcast are a pretty good example of this. In terms of GW races - they are practically brand spanking new and they are quite popular. GW is capable of making most of the factions in any of their game popular. Barring truly terrible rules, their visual design team is capable of reworking almost any faction into something exciting and they have proved this a number of times over the years.