No, this isn't an April fool's joke.  Source:  Special attraction added to fight expo

It will be best 2/3- The first event will be a grappling Match, the second will be a kickboxing match, and the third (if necessary) will be a full MMA rules match.

It says in the article that Buffer is a former Kickboxer, so it'll be interesting to see how he fares in the standup match & potential MMA match.

Rogan, as many people know, is a brown belt in BJJ under Eddie Bravo, and is an avid practitioner of Yoga (so he's obviously very flexible).  He also has a black belt in Tae Kwon Do, and has won TKD competitions in the past.

Personally, I think Rogan will easily sub Buffer in the grappling match.  Depending on how good a kickboxer Buffer is, the standup- only match will be very interesting.  Likewise, if Buffer wins the kickboxing match, and they go into the MMA match, it could be a classic striker vs. grappler showdown. 

IMO, Rogan will shit all over Bruce, but then again- I have a bit of a man crush on Joe.