AD Migration

Can anyone tell me the short term impact of having users receive DNS and DHCP from one Domain while being members of another? Background: We’re migrating users from Domain A to Domain B. We don’t plan on installing DC’s in every location where a Domain A DC existed. The plan is to leave the Domain A DC’s in place to serve up DNS and DHCP. There’s a two-way trust between the domains, and both domains second each other’s DNS. The plan is to eventually put a few Domain B DC’s out there, but there is urgency to migrate the users prior to that happening.

Thanks in advance.