I think the Nintendo Switch would most likely need the TV dock to connect the Nintendo Switch to a TV since Nintendo did not mention that there is a video port on the Switch's tablet like other non-Switch tablets like the Microsoft Surface Pro 4 which has a HDMI port on the side of the tablet to connect to a TV.
But, Nintendo or a third-party company may create a special USB to HDMI video cable, Remote desktop app, wireless/Wi-Fi video accessory like a Chromecast to allow the Switch to display video on a TV without using the TV dock, or being plugged into the wall's power, and rely on the battery for power like tablets.
I think the Switch may end up having third-party accessories like those TV/monitor cases which basically turns a game console into a game console laptop for playing away from home. The Xbox One and PS4 has a TV suitcase accessories to turn it into a gaming console laptop for gaming on the go.
But, the Switch will need to sell many units before it has these third-party laptop accessories. The Wii U did not seem to have any laptop monitor case from bigger companies because the Wii U did not sell very well, so if the Switch may not have a third-party accessory like a laptop gaming case if the Switch does not have a large userbase like the PS4 and Xbox One.