You've got everything ass-backwards. How exactly does this idea not seem far-fetched? The two companies are clearly competitors. Yes, not all pro-wrestling fans like MMA, but there is a huge overlap between the two, which is why Brock Lesnar immediately became the UFC's biggest draw.
The UFC is is in the business of putting on real fights, and associations with pro-wrestling would hurt their image. I'm sure that the WWE would love to get the rub from real fighting, because realisitically they have no chance of competing with the UFC in the long haul, but there is absolutely no chance of that happening.