Your doctor is planning on gradually weaning you off the Xanax, while at the same time, gradually stepping you up in doses with the Ativan. That's the proper way to do
it. As long
as he is planning on putting you on a dose of Ativan
that is somewhat comparable to your Xanax dose, you shouldn't have any major w/d issues.
If you're having problems with tolerance, and you take these meds on a regular basis (every day), then you may want to ask your doc about trying Klonopin.