Should we look to move to 64 bit Perl ( Perl 5.10) too?

It's hard to give a general recommendation without knowing the details.  The two main advantages of 64-bit perls are more addressable memory, and larger native integer numbers. Whether this is useful for you depends on the applications.  On the other hand, there are also some potential incompatibilities due to this — for example, see the discussion emulate 32-bit on perl 64.

But before migrating critical 24x7 applications, you would set up a test environment anyway, and thoroughly check for any incompatibilites... wouldn't you?