Riley being released wouldn't be a career killer at all. He's insanely over, with a good look, good charisma and ability to talk and he is okay in the ring. Plus coming off of a multi year WWE run. That means he can make good money on the independents, in TNA or in Japan. Hell, in Japan he would probably make more money than he does currently.
If Trent Barretta can be drafted into New Japan's yearly Best of super juniors tournament (A tournament for the world's best high flyers) then Riley if he went to Japan could be a star in their intercontinental division. Or a star in TNA.