Piper Jaffray analyst Gene Munster has again surveyed 7,700 US teenagers and has found that iPhone and iPad ownership among the teen demographic is growing rapidly, with iPhone owners nearly doubling over the last year. The survey had plenty of good news for Apple, as iOS devices remained heavily dominant in the buying plans for those who expected to acquire a new tablet or smartphone in the next six months. The survey showed strong interest in the iPhone and even stronger interest in the iPad, despite the fact that no new model is expected soon.