This is exactly what you think it is. Here's what Capom Unity had to say about the new Dead Rising content:
Super Ultra Dead Rising 3' Arcade Remix Hyper Edition EX + α is an all new, four-player co-op mode for Dead Rising 3 on the Xbox One. Play as classic DR heroes—yep, Frank and Chuck are back—and cosplay as your favorite Capcom characters both classic and recent. The cast of characters glimpsed in this trailer is absolutely stunning. Characters from Breath of Fire, Power Stone, Rival Schools, Dino Crisis…
I'm not sure how I fell about this. I mean it does look fun and I do love a lot of the Capcom franchise that are involved but this just fells like it cheapens the DR cast. I get that it does happen in an alternate world via the arcade game but...er...damn. Maybe, I will get it.
It's available now and it will run you $9.99 USD.