No, we don't HAVE to pay for the BBC. If you never watch live TV and only watch it on catch up, you do not legally have to pay the licence fee.
Im pretty sure that will change, every household will require a TV Licence even for BBC Iplayer catch up. Thats whats going to be proposed in the the charter (due end of 2016). Lots of paperwork online to show that.
A subscription service would be the best thing in my opinion, a la carte bbc content for about £8/m per household, but then why not buy a TV Licence and get it all for £11/m ?
Im sure someone in the corporation is thinking this way, we will just have to wait and see.