The extreme right wing would love nothing more than the BBC to disappear. Even the Conservatives would love to have the BBC hamstrung, much like PBS is in the US. If there's one thing I've learned in 25 years around the media, it's never say never.
People didn't expect Thames or TV-am to lose their licences back in 1991, but it happened. Channel 4 was not expected to ever be privatised, but it is on the agenda for this government. The BBC shouldn't be dismantled, but the right wing would love nothing more than to see it disappear. Vigilance is required.
The Tories know that there would be a public outcry if the BBC disappeared.
TV-am and Thames losing their licences is not the same thing. After all, there was still a breakfast programme on Channel 3 after TV-am lost its licence and, after Thames lost its licence, viewers in that area still got to see ITN, regional news, sport, soaps etc.