It really depends on what games you are thinking about buying. If you are an Indie fanboy, than I would say don't go past 1080p, seeing as most Indie companies don't have the money to go past that resolution. But if you are a AAA gamer with titles like COD or Battlefield, then they are definitely going to support the res. As for some gaming monitors for that resolution, I think I found a few for you:
https://www.google.com/shopping/product/12734305131198287805?rlz=1C1OPRA_enUS610US610&biw=1920&bih=947&q=21:9+gaming+monitor&psj=1&bav=on.2,or.r_cp.r_qf.&tch=1&ech=1&psi=ktVVVPn0I4uYyASdnoGICw.1414911443815.3&ei=1dVVVKbDHsa0yAS6jYLQAQ&ved=0CJoEEKYrMAA...