In an interview with WGD Weekly, Ken Shamrock revealed that he is interested in returning to pro wrestling for either TNA or WWE.

On being the first NWA/TNA World Champion:
"I was first approached by Jeff Jarrett. Because of the success happening in the UFC and MMA world, they wanted to try and bring that edge over to their organization, Total Nonstop Action. So they brought me in and they put the strap on me. The problem we ran into was that because I was training for fights, it was difficult for me to make all the shows. That was the downfall for me and TNA. I just wasn’t available to them like I should have been. I really thought it was a great fit and we could have done a lot of things, but unfortunately it was bad timing."

On a potential return to TNA:
"I am very open to that. With TNA, in the short time I was there, I didn’t have the time that I needed to work there. Now I have that time and I'm in great shape. I’m probably in better shape than I was back then because now I basically lift weights and do a lot of cardio. I don’t need to worry about keeping my size down for fighting because I'm not fighting. So yeah, I'm pretty much open for getting back. I just haven't had anybody reach out. I'm done fighting pretty much and I would love to get back into pro wrestling and do some stuff there."

TNA would sign him in a heartbeat

I wouldn't be against it. At least he can actually wrestle and also means something to TNA, being their first ever World Champion. I'd love to see Shamrock vs. Angle.

Long term, no, but one run would be nice.

It would be even better if he stayed at ... wherever he is.