Mixed martial arts is a big time business; the UFC is the big man on the scene, the guy in the Monopoly game staring down the last major competitor. The last major competitor is Bellator, which unlike other past MMA organizations, is backed and owned by a major corporation, Paramount, which provides financial security. The UFC has an arrangement with News Corporation, via the Fox Sports division, to air events on Fox, FX, and Fuel TV. Paramount owns Spike TV, and recently arranged to have Bellator on Spike. Other small outlets are out there, and some of them have even managed to get on national outlets; for instance, the World Series of Fighting had a trial run on NBC Sports Network.
So, unlike the Big Four sports (NHL, MLB, NBA, NFL), MMA is not a unified sport with one league, but rather one really big organization, with smaller ones surrounding it. In any case, though, MMA is big business. Fox Sports is paying roughly $1 billion per year for four major cards on Fox, as well as preliminary and other smaller cards on FX and Fuel TV. I don’t know what the arrangement between Spike TV and Bellator is, but I’m sure it’s of a mutual benefit. MMA events fill arenas, and have become a dominant force in Las Vegas, which once upon a time was center of the boxing world.
So, can MMA become a major sport? Well, it’s anomalous in many ways. Unlike the aforementioned Big Four, it doesn’t have a season, an off-season; rather it is a continuous, year round series of events. Its rough and tumble nature attracts a certain crowd, and turns off others. It has the potential, though, because of the pattern of events, because Fox advertises it strongly, and because Dana White has a vision for it, even if he has difficulty maintaining relationships on occasion, and sometimes runs his mouth a little too much.
MMA has supplanted boxing in the minds of many, largely because it requires an expanded skill set, and largely because the rules governing it require fighters to engage more.
So, in answer to the question I posed, I suppose that MMA has the potential to become a major American sport if it can continue to advance and become more mainstream; that road, though, will probably take a while.