Outlook 2007 profile update after move to Exchange 2007

Hi,

We are transitioning to Exchange2007 and currently we have:

We have:
Exchange 2003 Back-End server.
Exchange 2003 Front-End server separate hardware. (which I want to replace now with CAS).
Exchange 2007 Mailbox server with CAS on same server.
Exchange 2007 CAS server just installed separate hardware.

I cannot uninstall Exchange CAS from Mailbox server role yet until i make CAS work properly.
I cannot uninstall Exchange 2003 Front-Edn until i make CAS work.

New CAS server we would like to name owa.company.com for resolution, but currently we have our Exch2003 Front-End server DNS pointing to owa.company.com.

So if we keep the name the same and make the replacement of Front-EndExch2k3 with CASexc2k7 all outlook profiles will not need to be updated, correct?
Or we should create new DNS pointer webmail.company.com and Outlook2007 Autodiscory automatically figure itself out?