I had seen my last T for 5 years, then she decided to close her private practice and move out of state. At first I thought I was OK with it, but then I got mad at her and felt like I was being abandoned (which I was). She gave me about 6 weeks' notice, but I only saw her every 2 weeks so I saw her 3 times before she quit.
I found a new therapist and she helped me work through the reality of my T leaving. It did get easier to deal with as time went on. I know that she quit and took a new job to improve her life, but it felt like she ruined mine for a while.
It's been about 18 months now, and I'm no longer mad at her. Just a bit annoyed.
Hang in there. It should get better with time. At least you already have a new T picked out. Hopefully this T will help you to deal with your current T leaving.