Only if they made sense and there's a good reason for a group to be there. Personally, I'm waiting for a good successor to Marcus as a super mutant companion (Fawkes and Lily didn't cut it, Fawkes was a different species and didn't have a enough depth and Lily was annoying and also without depth). I couldn't care less about cannon fodder super mutant enemies, especially because super mutants will be extinct eventually with no means of reproduction (both species). Anyway, nothing suggests Super Mutants would fit as an enemy and the voice actors and characters that have been detailed (likely the only ones) don't indicate a mutant or mutants.
Keep in mind that the Super Mutants would just use the voices already in the game files from the core game (like the Mr. Handys, Gutsys, Orederlys, Robobrains, and Sentry Bots in Old World Blues), so a voice actor wouldn't have to be listed. Also, the trek through lonesome road is supposed to be treacherous and dangerous. Super Mutants tend to prove that they can survive in much more dangerous places than humans. I think the devs could figure out a way to incorporate them.
And as for a Super Mutant companion with no depth, what about Dog/God? He's pretty dang awesome.
Edit:
I think possibly recycle these creatures from http://fallout.wikia.com/wiki/Van_Buren_creatures.
For example, http://fallout.wikia.com/wiki/Mutant_cannibal.
For example, http://fallout.wikia.com/wiki/Mutant_cannibal.
I found the enemy I want.
"Mutant cannibals are one of the results of environmental disaster in the Grand Canyon"
It fits so well with Lonesome Road! I know the Grand Canyon is not the Divide, but the Divide is described as having canyons, and suffers from some kind of disaster (maybe environmental, is going by the research Ulysses did in Big MT). AND, they would qualify as mutants! Just stick the generic sound bytes of Feral Ghouls/Lobotomites on them and you have a new enemy!