I have to say RTS is generally going by the wayside. Which is unfortunate because it has and probably always will by my favorite way to game.
I think there's a few things that contributed to the steady decay of RTS:
Phone games - A.D.D. generation gets their gaming fix through all the quick playing games on your phone. No need for a high-end gaming rig, which brings me to my next point.
Technology escalation - RTS has often been one of the most demanding/least optimized gaming vehicles and I think it turns a lot of people off. You could just go get a whole console and a couple of games for the price of a cutting edge graphics card that lasts 2-3 years before you have to upgrade again. Seems like every time a new RTS is released the graphics emphasis is way overblown.
Complexity - While shooters have gotten ADS/crouch/cover systems etc over the last 10 years and RPGS have gotten crafting(and a bunch of other stuff), it was all implemented more smoothly than all the new additions to RTS. RTS has gotten increasingly complicated, more difficult to balance, and less accessible.
I'm with a few others on here. I'd like to see AOE4, or just a really solid remake of AOE1. And unlike everyone else on here I'm not looking forward to DOW3 all that much. Looks like they've changed too much again and are continuing on the trend to add more super-weapons into the game, which is what killed DoW2 for me. I don't see why they couldn't have just done a re-vamp of DoW2 with a complete balance overhaul add the Tau and Necron as a first release and then add sisters of battle and dark eldar for 1st xpac, then add Mechanicus for a 2nd expansion. Then they'd have a really solid complete 40k experience.
If RTS is going to make a come back a developer out there needs to take it back to it's roots. Simpler combat with a very solid rock-paper-scissor balance system , satisfying base building, and a solid minimally buggy game engine. Graphics also need to be moderate with ways to scale it way up or way down (without the game looking awful). I'd also like to see a new RTS released that only starts with 2 factions. Each faction added makes the game exponentially more complicated to balance.
just my 2 cents
I agree man, old school RPG and adventure games have already proved to be worth the investment (PoI, Dreamfall Chapters...) so why RTS can't be the same?