Domain Migration

I am currently running a Windows NT Server domain with Exchange 5.5 running on one of my BDCs. I plan on upgrading my NT PDC to 2000 AD and leave my Exchange 5.5 on the NT based BDC for about 2 months before migrating it to Windows 2K with Exchange 2000. Does anyone see any potential pitfalls that I could have with this scenario. Thanks in advance.