Nah, if Oda would to that it would be a slap to the fans. Seriously ever since Mihawk said, "Surpass this sword, surpass me" and Zoro said he would never lose again, their last fight is got to happen, it's like fate.
No it wouldn't, it would be a cruel twist.
You can't promise to not die. and by killing the murderer of you master you've also surpassed him in a way. Besides I can't really see how a Zoro vs Mihawk fight would work out. They've spend 2 years together and I know they're both competitive but would they just meet on the end of the grandline somehow just before going to raftel and have a match ?
I doubt Mihawk would take orders from the WG to hunt down the SH's since he turned down fights multiple time in people he took no interest in. After spending two years with Zoro I doubt he would be willing to crush their dreams at the last moment.
Only thing I can see happening is that BB's crew would be there till the end for the final fight for Pirate king, his strongest swordsman is Shilliew and he is bound to fight Zoro. But it would be a stupid final fight if Zoro already is the strongest swordsman.