I think Gordon would butt scoot. While I don't know if Roger could take him down point blank I don't see Gordon outwrestle him either.. and he'd probably would want to avoid to put himself at risk of random scrambles against a guy who especially nogi was known to capitalize out of this situations like few others.
Then what happens next is hard to tell, at least in details. Roger is a grappling genius and I'm sure he has his own, very valid answers to the whole new school meta, but to say if he's able to pass him, or to entirely avoid the many risks or ashi garami/HH etc. it's, as I said, hard to tell. The only non-technical, mild prediction I can think of is that at this point, after the Buchecha match proved not even the rust and an absolute moster like Marcus stopped him, it's safe to say that if somebody else did survive or even beat Gordon, then Roger can do it.
That said, I think before even think about this Gordon should clean the house from active competitors, like the same Buchecha or Pena. And I think he needs to start focus on MMA on some not so far point, if it's his real big goal. So it's probably never gonna happen.
