I'm hoping that Exum is the Alpha Dog that he was drafted to be and he ends up starting at the PG position. I think that his potential to physically dominate smaller guards would make that his best position moving forward.
I also think that you keep Burke if Exum outplays him for the starting job and play him off the bench and in combo with Exum and Burks.
Having two young, starter quality PGs running the offense at all times makes a lot of sense when you consider how important the PG is in a P&R heavy offense. Especially at what Burke is going to cost.
Best case scenario is that Exum lights it up early and often and forces his way into the starting lineup. Burke fills in for him off the bench and there's not a significant drop-off in production since Trey will be matching up against many 2nd unit players. His contract isn't bad and he has leadership qualities that I'd love to see coming off the bench. I think that he'd be a guy who would force other bench guys to play up to their potential. Give me Gobert, Tomic, Evans, Hood, Burks and Burke off the bench. . . that gives the coaching staff some great rotation potential. Much better depth than they had last year with Marvin, Jefferson (even though those two were starters and getting too many minutes, I still consider them depth players), Biedrins, Rush, JLIII and Garrett.