You have no idea how extradition works, if you are extradited to one country, and that country tries to extradite you to another, the first country is required to have an additional extradition hearing unless that move was an established pre-condition.
The Swedish wouldn't be "extraditing" him to the USA, they'd be "lending" him as part of the ongoing investigations into Wikileaks.
See: https://justice4assange.com/us...
What are the chances of the USA ever giving him back after Sweden drops its charges? Slim/none.
What would the UK be willing/able to do about it? Probably nothing. Nobody's job is on the line (they're all following the law) so, hey, bad luck Julian.
This interview in London is just ass-covering by Sweden to keep the case alive. Don't expect anything to come of it.