Current situation:
PDC: OES2 SP2 32bit
ADC: OES2 SP2 64bit

End goal:
Get ADC and PDC to the latest version (OES11 SP2).

As newer versions of OES only run on 64bit, I need to get rid of the current 32bit PDC. My idea is to make the current ADC into PDC, then remove the old 32bit PDC and install a new 64-bit system as ADC. Then I can upgrade the servers following the supported upgrade path.

I've read the OES2SP2 docs and seems that what I need to do is:
1. Transfer FSMO roles from current PDC to ADC
2. Migrate DNS from current PDC to ADC

Both these steps are described quite well in the docs, but I have some doubts about DNS. After I migrate DNS from PDC to ADC, will DNS service continue to work on the old PDC or not? TID7008036 seems to indicate that the answer is no (since after migration the old PDC is now ADC). So I will need to be prepared to change the IP address of DNS server in all the places where the IP of old PDC is hard-coded? Or is there a way around this?