if burgos is doing an ok job, why would they boot him? i don't think the organization could tell you what's going to happen until they see mac face big league hitters. he'll probably come up and do some low-pressure outings. if they go well, and burgos falters, then you'd have to think that mac would take the job.
in your case, if you have a spot to burn, mac's a fine seat-warmer.