What's the hold-up with the migration?
Also, have you confirmed Linux (whatever distro you choose) will actually work in your environment? I've heard of some small scale deployments of 100% Linux environments (up to 30 PCs) being very, very successful, but anything larger tend to get saddled with Windows-only application requirements, especially in the area of accounting software, business management software, etc. (It's not the general Office software (Word processor, Spreadsheet, etc) that's the issue, it's the 100's of little legacy applications or customer written stuff that's the issue).
Having worked for a manufacturing company in the past, even some of the PLC software was Windows only! Let's not get started on the software for the lab equipment** or PABX!
**. The software would only run on Windows 2000 SP3, installation of SP4 would break the software, in that it would only run as the actual "Administrator" account, not even as an account in the Administrators group. No go on Windows XP, either.