Possible MUTO nods

The reason they shouldn't do that is because it diminishes the importance of the characters Gigan and Megalon, plus Legendary won't buy the rights to Gigan and Megalon just to retroactively name two completely unrelated monsters after them. The M.U.T.O.s are their own original characters, they don't need to be turned into incarnations of classic monsters, even as just a nod to those monsters.

We might hear the name MUTO (Massive Unidentified Terrestrial Organism) to describe the creatures a few times, but eventually they would get their own names in the Legendary universe.

Unoffical Names for Mutos in G2014

Male: Hukmuto

Female: Femuto

These were names created by fans.

Those weren't really fan-names. They were names created by Legendary in the original script. "Hokmuto" was short for "Hokkaido M.U.T.O." because the male was originally to be discovered in Hokkaido, and "Femuto" was obviously short for "Female M.U.T.O." In the final script they just called them both M.U.T.O.