The show is called "the office" not "dunder mifflin's office"
As long as some sort of office is around, the show can go on. I question though the documentary crew. Are they trying to film the workings of Dunder mifflin, or of the characters that worked at Dunder Mifflin?
I think because its tha latter that the crew will follow the characters. I see a few scenarios:
1)Charles angers the entire staff, all of whom quit and go to MSPC and they all have a new office park. business carries on as usual. The show either continues with MSPC, or Dunder mifflin buys it, everyone goes back to the old office, and Michael is given charles' job, but retains regional manager as well, so he stays in the Scranton office.
2)MSPC fails miserably, after siphoning more DM employees away, and the show ends.
3)MSPC fails, David, realizing the mistake in hiring charles, brings everyone back, with Pam in Sales (occupying the desk that jim sat at when ryan has jims original desk) and michael with a pay raise, or with added responsibility too.