Oh, the mercs are actually mutons? Guess that explains why they're just as tough as them.
Yes, but in a confusing way.
See, Muton is not a species; it is an augmentation type. You probably could take a human, cyborgize them heavily, pump them with magical steroids and presto! you have a Muton.
So, I think Mercs use the same augmentation technology - effectively becoming Mutons - but they are not of the same species as original Mutons.
(This is mostly my speculation, based on various conversations with Dioxine.)
I just assumed the star gods stopped making floaters. They were a lot of work in return for poor soldiers that even conventional Earth weapons took down easily. They weren't bright enough to take much advantage of flight, and anyone can make a cheap grav harness anyway.
Floaters currently reproduce themselves, using Star God tech (much like Factions on Earth). There is a whole planet of them and they live in relative prosperity (for a heavily polluted world).