When I upgrade to BES 4.0, will the 7510 handhelds running version 3.7 software continue to work? Or will I have to re-activate them on the handheld end?

Must the handheld software be upgraded? Or will 3.7 handheld software work with BES 4.0?

Any insight would be helpful. Thanks

Yes they will continue to work. However if you which to make full use of some of the BES v4.0 server capabilities, then the devices will have to be upgraded to a 4.0 device code.

ok, but will the 3.7 devices need to be reactivated? Do I need to send them an activation password from the BES server?

It's not necessary....since you'll be keeping the same SRP ID & Auth Key; BES Service account&mailbox.
If you are change any of these then a re-cradle would be in order.

thanks dev