That's a couple possibilities yes, but for me when I hit end-game Mythics alone aren't going to be enough.
Also people have been offering solutions that they would like to see. Crafting being one, and Sirrian commented on that. I'm of the mindset though that people getting those last few troops they need, isn't going to make them stick around longer. They will have "completed" the game for the most part at that point. Still think it's a good idea though. I personally just want content for me when I hit end-game.
When you're low-level to mid-level, 1 type of troop isn't all that you're chasing. You have so much to do. So for me just getting Mythics wouldn't satisfy me.
They put a restriction on rewards, no need for souls or stones currently, a restriction on leveling up, etc. So yeah being at end-game is pretty grim in terms of having something to look forward to and work for.