Maybe, maybe not. Depends how much material they have on him or anyone else in NXT. Assuming they have a scan of him (and depending on schedules, who knows if they even have that yet?), they still have to build the character model, capture his moves, taunts, and entrance, record ring announcer and commentary audio, etc. WWE might have made the call to cut Nash Carter from the DLC too late to even consider it.
I think the easiest replacement would've been some of these MyFaction-exclusive characters that are 100% done and work fine. Guys like Godfather, Mankind, Dude Love. Or if they wanted to go current, grab the Zelina Vega model from 2K20, touch it up a little, and throw it in. All the other extra work has already been done.
In the end, we can all agree that MyFaction cards are a terrible substitution for a character. Somewhat related - they're also already removing creation parts tied to MyFaction-exclusive versions of wrestlers, so they're setting the bar for where things are headed.