Overwatch will get a heaping helping of new maps soon if all goes according to plan. Game director Jeff Kaplan stated on the game's forums that the dev team is currently working on three "standard" maps (meaning they'll be available via Quick Play and Competitive modes), three "non-standard" maps that won't go into the Quick Play and Competitive rotations, as well as "a few other experiments."
"While something could always change, all 3 of [the standard maps] are looking likely for a release this year," Kaplan wrote. "Hopefully this will satisfy some of what you're looking for. We want to play on these maps as badly as you guys do. We'll work as fast as we can!"
Personally, I'm most interested in these "experiments" Kaplan is referring to. I'd wager that the "non-standard" maps are Brawls or holiday-themed arenas, but who knows what those experiments could be. Or maybe I've got it backwards, and the experiments are the brawls - but then what are the "non-standard" maps? It's all so mysterious!