Aikido seems to be in decline as MMA grows. MMA means Mixed Martial Art but there is no 'mixed' in it any more - it is just what it is - a single entity. Perhaps a way forward for the traditional arts is for MMA to put the art back into what they do. Thus, MMA could teach some Karate, Aikido, Judo, Taichi - whatever is available - but not at random, but rather, whole lessons dedicated to that art so that people could really get a handle on it. I got this idea while chatting with an MMA guy, some time ago, who was lamenting the lack of 'connection' to tradition / past etc. Anyway, maybe MMA holds one of the Aikido revival keys. If MMA were to start doing that, maybe in the long run members would join independent Karate or Aikido clubs to learn more. Just a thought ... but I do know of one Jujutsu school that has recently adopted Aikido into its syllabus (and gets an Aikido teacher over to teach).
It depends on your part of the world. I don't see any decline where I'm from. In fact I don't think there is any decline it's just popular to say that for some reason. As for mma, it's still pretty much mixed although thanks to the UFC rules it can be described now as "wrestling and anything else".