I'm not certain we will have that luxury, as it will be tricky enough with versioning to get the copied missions to work (and we'll probably have to do some hand tweaking behind the scenes to get them to acknowledge Holodeck).
Many times Tribble is on a different codebase than Holodeck, so the feature you're asking for isn't as cut and dry as it may sound.
So for now, the reality is that missions will have to be remade when the Foundry is turned on for creation on Holodeck.
This is one of the reasons I have been trying to tell people to not pour their heart and soul into the Foundry on Tribble. Tribble is a test environment. Use Tribble to see what you can make and learn the tools so you can know how to make it. Save your good stuff, your real stories for Holodeck.