Will removing developer devices break apps with old UDIDs on Provisioning profiles?
I don't think that Apple reaches out and revokes certificates on devices when you wipe the slate clean, but they would be in their right to do so and they have the capability to do so.

Most likely, those devices will work until a certificate (or intermediate in the trust chain) expires. Or until the "testers" remove the app or wipe the device or remove the trust profile.