Hi @tonigary7262 Welcome to the community, your Telstra TV will still work on a TPG NBN service if you still have a valid Telstra ID.
You don't need to be a Telstra broadband customer, you will however need to reactivate the Telstra TV box to the server once your connected to your new TPG NBN service.
Hi @tonigary7262 there's a good chance your Telstra ID will be valid for reactivating the Telstra TV, I can confirm that the Telstra TV will work on TPG NBN however I've got no way to test it with a non active Telstra login.
I wouldn't be basing my broadband provider choice solely on a device that can have it's support dropped without notice, Telstra has already stopped supporting the T-Box, there are other alternatives that will work better than a Telstra TV and be more future proof, such as an Apple TV.
Hi @tonigary7262, in the event that your Telstra ID is canceled and your TPG NBN service is activated, you can get a new Telstra ID for free and keep using the Telstra TV.
All you need to do is register a new one here: http://media.telstra.com.au/home.html > Movies. The only time you will need to pay anything is when you watch a movie.
Let us know if we can be of further assistance. Thank you.