I would rather them not recast Burke. Like him, love him, dislike him, or hate him, I can only see IW in that role. Burke is who he is because of the portrayal by IW (imo). Some day down the line (if Shonda doesn't get the show cancelled with her exceedingly stupid love twists) maybe forgiveness will happen and the actor will come back to the show. I'd love a future surprise cliffhanger of Christina opening the door to see Burke (as played by IW) standing there.
In the meantime, I agree with whoever said to just bring on a few new characters. It's getting too incestual as it is with all the bed hopping between just a few characters. Let's have some fresh faces and fresh storylines. And pump up Bailey and the Chief's parts.