Just as the title says, the Event Store TCP client is being deprecated. This means that the TCP client will occasionally receive bug fixes, but any new features of EventStoreDB will be available through the gRPC clients.
The TCP protocol will still be available through the LTS versions of EventStoreDB: currently 20.10 and 21.10, and will be fully functional.
It is possible to use both the TCP and gRPC clients in the same system; for example, you could use the gRPC client for the new database features and the TCP client for older functionality, then gradually update the rest of the system to be compatible with the gRPC client.
We recommend you start planning your upgrade to the gRPC right away. We have documentation here explaining how to upgrade the framework and a webinar with Oskar Dudycz performing a live migration here. If you need more help, feel free to ask on our Discuss forum or contact us and we will do our best to help you.