If it has its own SIM then it will have its own phone number as well. If you still want to use is as before, i.e. get messages via wifi, then you can still do that. Just don't use the new number if you have no need for it.
The main thing to be aware of is using mobile data through the SIM because if you go beyond you plans allocation it can cost as much as $10 per gigabyte (depending on the plan) for any excess data.