According to Dave Meltzer from Wrestling Observer Online, World Wrestling Entertainment has made an offer to Brock Lesnar to face The Undertaker at WrestleMania 27.
It has also been said that Brock Lesnar is not going to say anything publicly for about two weeks.
It is still not clear if this would even be possible as it is likely that Brock’s contract will not allow him to go to a different company and work even for a one time deal. Unless Vince pays the UFC to use him.
Further reading: World Wrestling Observer