The problem though is that small joint locks are illegal in MMA rules - so no wrist locks or finger locks. The taping of the wrist/hand inside the gloves also makes it extremely difficult to apply. I can see something like a variation of iriminage being used but it might be mistaken for Judo.
Even if Aikido were used in the UFC, it won't create a renaissance in Aikido because of Aikido's philosophy. MMA fans just wouldn't have the patience to practice it without hard sparring. Similarly there is very little obvious Aikido techniques that can be amalgamated into an MMA gym. Alot of people go straight into MMA without coming from a traditional martial art or single discipline background.
Judo is far easier to amalgamate into MMA because MMA has a strong grappling base in collegiate wrestling. Judo is effectively an alternative to wrestling.
I would love to see Seagal go back to his roots; out of interest which Seagal film do people think is best for Aikido?
Actually wrist locks are legal, but few fighters have developed the ability to actually use them in competition while wearing those gloves and covered in sweat. If I recall correctly the closest
I've seen to an Aikido "locking" technique in an MMA fight was via Shinya Aoki around the 2 minute mark in the following clip:
I know Henry Ellis's son is a very good Aikidoka and competes in MMA in the UK and has incorporated things so that may be the best source for opinions on the subject.
Finger locks may be legal as well. I know that you have to grab a minimum of three finger to peel a grab off, so maybe it's permitted to apply a lock to those fingers as well.
I seriously doubt we're ever going to see the introduction of non-sport martial arts into the MMA curriculum. A fighter simply doesn't have the time to train Muay Thai, Boxing, Wrestling, Jiu-Jitsu and then add an art with a hefty learning curve to that.
You of course have guys from TMA backgrounds like Lyoto Machida and his family's version of Shotokan Karate. But he competed in tournaments so adapting it for MMA wasn't as complicated.
Also, you have to keep in mind that the person in the ring is competing against another highly trained fighter. Applying an Aikido/Jujutsu technique on a non-athlete is one thing, but trying it against an athlete that knows how to fight is something entirely different. Visit a BJJ school and train for an afternoon if you get the chance. It's a very enlightening experience.