Portable media players with video capability are expected to outsell audio-only devices by the end of 2008, according to a study from In-Stat.

The report, estimating both unit sales and revenue throughout 2011, indicates overall demand for MP3 devices will stay strong.

Currently, only 11 percent of the survey respondents said they would buy a portable media player mainly for its video functions, even those who are purchasing a video-capable model. However, the number is expected to grow very quickly as the price goes down and video quality improves.

The study predicts the overall unit shipments of MP3 players and portable media players will exceed 275 million in 2011, compared to 182 million in 2006.

In the recent In-Stat survey, 52 percent of 2,408 respondents had an MP3 player or PMP.

Meanwhile, music-enabled cell phones are not as competitive as MP3 players, but the niche may grow as some consumers search for audio-only playback capability as part of cheap, multipurpose devices.

As for the mobile phone, a study from SNL Kagan shows that nearly 85 percent of the U.S. population will own a mobile phone by the end of 2007, and will reach 100 percent by 2013. In fact, Kagan says the number will exceed 100 percent as some consumers own multiple mobile phones for different purposes.

Total U.S. wireless revenue is expected to reach $253 billion by 2017.