If you have 'traditional' Sky that you watch through a TV set, you still need a licence. Sky itself is just the platform, with channels sourced from various places - the ones owned/provided directly by Sky are obviously included, and the free-to-air channels should be by-the-by; but the 'terrestrial' channels they also transmit through their platform do require a licence.
In fact, I'm not sure quite how it works and how the law has caught up with new technology options, but I think that, even if you had a way of blocking all non-Sky channels through your Sky box, you might still find that owning and using a traditional TV set to watch telly technically requires a licence.
I'm one of those very rare people who thinks that, in spite of its many, many faults, the BBC is well worth the licence fee for what we get from it - but it's anachronistic nowadays - and grossly unfair - to charge people to watch any TV and give the money to the BBC.
I don't know what the plans are for when the licence fee ends, but a subscription model for those who want to receive BBC services would be much fairer - and we would certainly subscribe. I just don't know how they will restrict it to subscribers only, as the whole BBC infrastructure is currently based on everybody having free access, because everybody has already been made to pay up.