Hi MalikShahab
My understanding is that Veritas is looking to move to subscription based licensing going forward. Perpetual licensing can be maintained, but it is possible that without subscription licensing you may not be able to access all features.
I would suggest talking to your account team (or partner) to see what the best option will be for you - I don't think there is a hard and fast rule that one is better than the other (except as indicated above access to some new features).
If you exceed your licensed limit, then at present everything will continue to work. Expect a true up at the next licensing renewal period to ensure you are correctly licensed.
Cheer
David