There is a machine called the Retron 3, released last year by the gaming hardware folks at Hyperkin. That thing was a combo Nintendo Entertainment System, Super Nintendo and Sega Genesis.
What comes after the Retron 3?
The Retron 2. A little weird, right? But I guess some people only wanted the NES-SNES combo.
Also in this video: a prototype of the Comrade gaming helmet, a combination real military helmet and gaming headset. They're doing that one partially for the "cool factor." Hey, whatever keeps your head safe from shrapnel while gaming, right?
There's no release date the Retron 2 or Comrade, but you'll eventually be able to buy both from Hyperkin.
UPDATE: As some commenters have noted, a machine called Retro Duo does something similar to Retron 2, so consider that one too!