How about they're both doing well, and they're not really competing to put each other out of business, so who the **** cares? There's plenty of room for multiple sports. Is football dying because of basketball or hockey or baseball? No. All the sports have their fans. Some fans watch a million sports. I watch both MMA and boxing. Unless you're an idiot, it's not too hard to follow two things. This whole, "MMA will be forgotten, boxing rules!" makes no sense.
All those saying "MMA" has been around since the Greek olympics. Granted. No doubt it has been. But what happened? Why the ebb and flow of it's popularity? Okay, it was big during olympics in antiquity. And now it's big some 2000 years later? And I'm supposed to trust the sentiment "MMA will be around for a loooooooong time". What is this based off of? Certainly not it's historical success. It can't be claimed, "Well, mma is a new sport.. it's just catching on." Because, it can't be both a new sport and have a history that stretches back 2 millenia. Look at pro-wrestling. It didn't start as pro-wrestling in the sence of choreographed matches. It started as catch-wrestling. Some submissions very analogous to holds we see in mma today. Why, some hundred years back, when it surfacing... it was eventually co-opted into pro-wrestling? The history of mma and the history of catch wrestling in the States (as well as other parts of the world) shouldn't lead anyone to conclude, "yeah, but THIS time.... it is going to last." Catch-wrestling started churning out boring grappling matches. The fan base started to dwindle. In comes scripting, out goes technical subs. Saying that mma is going to trump boxing is tantamount to saying that football is going to trump running. Both of the formers heavily incorporate the elements of the later. Remove the later, remove the viability of the former. In both cases, the later has a more consistent history... it's the former that ebbs and flows.