I have an old v1 cab running v5.0(26)

It is currently running 45 IP Phones.

It has a v1 VCM32 card with 16 additional channels licenced.

Would I need to add IP endpoint licences if I upgraded the cab to a v2 running v9/v10

Talk to your Avaya SE, as this is tricky. there is no migration like you would get when upgrading to a new release....

If you upgraded, you would receive 4 IP endpoint licenses per VCM channel licensed...but since you arent upgrading, that wont happen automatically.

You will probably need to do a special bid to accomplish this...which will require your CAM and SE to work through it with you.