BBC 3 is a pretty good test bed for new programming. The life cycle generally goes like this
First airs on BBC 3. Proves to be very popular.
Moves to BBC 2. Ratings continue to improve.
Gets promoted to BBC 1. The Daily Mail gets wind of it and complains that it's puerile.
Show is cancelled.
Seriously though, they're going to replace BBC 3 with a +1 channel for BBC 1? The BBC has always been very keen on promoting the iPlayer for catch up.