Massive unidentified terrestrial organism

The MUTOs will most likely not appear. I believe Legendary won't focus on them anymore as the rights to other monsters have been given to the studio. 

I kinda agree with SCI-FI KING25. I hope that Toho obtains the rights to the Mutos though. I would like to see what Toho could do with them. Also, whats a Kailua?

God I hope they don't come back.

I don't think there is any need to include the M.U.T.O. in the sequels. They were only used in the first place because Legendary didn't have the rights to any of the kaiju and had to make their own. The M.U.T.O.s got their time in the spotlight as the main antagonists in the first film, and now it's time for some of Godzilla's more recognizable allies and enemies to take over.

Now don't get me wrong, I liked the M.U.T.O.s and I'd love to see them return in some other media, like comics or video games, but I think their role in the Legendary series has been finished.

Kailua was a typo sorry I meant kaiju

Kailua was a typo sorry I meant kaiju

The most I can see them do is return to be cannon fodder to the bigger stronger monsters Legendary has now

Loved the a MUTOs. It would be great to see them again.