It'll take several more years.
You see, the way most diets "go mainstream" is actually through fast-food and junk-food companies' sponsorship. Once something can be labelled "Perkins' Diet Friendly!" or someone can make a "Fish-Diet Ready-Meal", said diets "catch" on, as they receive a lot of publicity and studies into them can be funded by these companies, who now have something to gain.
And the junk-food industries are trying to do it with Paleo. The problem here is, of course, that their manufacturing methods, ingredients and general idea of what food IS does not work with Paleo. So their "Paleo cookies" and "Paleo read-meals" get slammed by the Paleo community. After doing this a few times, they're beginning to see us as "non-consumers": a population they won't even bother catering to. Without them funding a few adverts and some research, the general population won't show an interest.
However, Paleo will grow. Allow me to use an awesome analogy: Paleo is like a zombie apocalypse. One Paleo in a community regains his/her health. Their family sees how much good it has done and tries it. Their friends and their family's friends see how much good it's doing these people and try it. Their friends' families see how much good it's doing THEM and... you get the picture. As the community grows, we'll find more and more Drs and Nutritionists adopting Paleo viewpoints as they would have tried/witnessed it themselves. These people would get involved in further research, studies...etc. We just have to do it WITHOUT corporate funding and with, to be honest, all the opposite: corporate backlash. McDonalds, Nestle, Kraft... They aren't about to give up their loyal consumers. We'd have "counter-studies" and an explosion of "you're not eating enough bread"-style warnings/adverts.
But still, you can't argue with good health: most people don't "quit" Paleo and those who do often return or incorporate it in their new diet. Someone who's Paleo and healthier than ever won't turn away from it because their vegan friend or a Warbutons-funded study tells them to. And, as the zombie-expansion takes place, we'll see a quick turnaround where Paleo suddenly becomes accepted, then, to some extent "normal".
So yeah, a few more years.