I'm not expecting there will be.
This is merely having fun at the expense of a temporary bug which, although we might enjoy it, is not something the Admins may want to preserve in Combine lore by having to explain every six months with a series of answers that run something along the lines of:
"No, that Achievement was just available for two weeks in Year 18."
"Why? 'cause it was a bug, that's why."
"Are we gonna re-enable the bug so you can shoot a zombie Vornskr? Not on your life. We have more important things to do."
"I don't care if Rumble Stiltskin has an 'I Shot a Zombie' achievement badge and you don't!"
Yeah, that'll get old real fast. Still, live in the moment.