Fans’ prayers have been heard, Overwatch is going to get 3 new standard maps (i.e. available in Quick Play and Competitive Play modes), likely coming out this year. So far, we’ve only seen two new arenas since the game’s launch in May 2016. However, in a forum thread about the frequency of new maps showing up, Blizzard’s Overwatch director Jeff Kaplan said:
We currently have 3 maps in development, all past the initial playtesting phase that are "standard" maps (QP/Comp). While something could always change, all 3 of those are looking likely for a release this year.
He also mentioned that they have 3 non-standard maps in development (not available in Quick and Competitive Play) as well as a few other experiments. While the release dates are still up in the air, the team promise to work as fast as they can.
Overwatch is still in the seasonal event called Uprising, which is going to last until May 1, 2017. As usual, it comes with a new story-driven PvE mode as well as a bunch of goodies.