Plenty of people will stay on MEAN, if they've already shipped a solution that works and have the staff to maintain it there's no urgent need to switch.
From what I'm seeing around meetups though, React has definitely got a lot of momentum for new projects and rewrites. Will it last any longer than Angular? Hard to say. I think React has become popular just as people have got some deep framework fatigue, much like jQuery did back in the day. So React might enjoy a longer period of popularity.
Also suspect graph databases will be getting an uptick of popularity.