Questions about migrating to DDNS

[Her, Andre]

All,
We are building migration plan for moving from a mix of bind 4.49 and 8.xx to the latest bind9.xx
with DDNS.
DHCP is the next migration.
A suggestion I have to review is as follow.
While the migration, leave the 5000++ users still use the DNS servers they already got from DHCP. local config etc, but configure the old DNS server to forward the request to the new servers.
Once the migration is done, change their configuration both manually and trough DHCP.

Will that be working, while the forwarding,  will the old bind4.49 not be rejecting the new SRV record and the dynamic update ?

Many thanks in advances
Andre Her
BlarenbergLaan,2
2800 Mechelen
Belgium
Tel : +32 (0)15 78 6887
Fax: +32 (0)15 78 5405