At this point, you might think that everyone in the US who wants a TV has one. But the population is growing, and there will be more than than 50 million additional US TV households in the next 40 years, according to new data released by Nielsen Media Research.

The question is: What will media-viewing habits be like 40 years from now? We may not yet have our own personal robots to change the channel, but custom-tailored TV lineups are likely.

The way we watch TV now is likely to shape future viewing habits. This includes watching TV while online &mdash something 70% of Internet users do now..

Beyond viewing habits, tech trends may also blend TV with other media. Although the number of people in the US who get their TV via the Internet is currently low, in 40 years the potential to deliver targeted ads via IP may have changed the TV landscape radically. With TV delivered alongside the Internet, viewers are likely to be less engaged exclusively with either one.

As such, the best strategy for TV marketers is to assume that attention waxes and wanes during media usage and that full engagement is no longer a realistic expectation. Add another 50 million TV households, each consuming other media at the same time, and the need to switch expectations becomes clear.

Prepare for TV's future by learning about today's multitasking consumers — read eMarketer's Multitasking Consumers: Distracted or Connected? report.