It depends on how long, but if they were leaving in less than a year, then no.

My first T, whom I saw at my university's clinic, was in a doctoral program meaning she would only be at the clinic for one year. I didn't know this at first, and about halfway through the year, she realized she had neglected to mention that she would be leaving and apologized profusely. (I was not and am not upset with her, just to be clear.) She left right when I felt we had JUST started making progress. It takes me a long time to trust a T. So if a T was leaving in less than 1-2 years, I would not see them.

Silver lining -- when my old T left, she gave me a name of a therapist she knew whom she I thought I'd get along with. That T is now my current T, and she was right, we get along splendidly