Ethernet was added to the HDMI standard since version 1.4 and most cables today support that. If your TV is connected to an already networked box via a HDMI cable, chances are that it won't need a WiFi connection to go online.
Also, it could connect to an open WiFi without telling the user since it wouldn't need any input to enter credentials. It is becoming a lot harder to remain offline, at least with TVs.