Every time I hear this argument I don't know if to laugh or to cry.
Assange himself pointed out that it is much easier to be extradited to the US from the UK (which extradites to the US almost anyone for pretty much any reason) than from Sweden (that as far as i know very rarely if ever extradites to the US).
If he was really afraid of being extradited to the US, he would want to be in Sweden rather than in the UK.
The UK can send him to Sweden, saying they complied with EU rules. The UK can then relax, and not deal with the wrath of Australia being pissed off - an ex-commonwealth country.
Once he's convicted in Sweden, he can serve the two-months or whatever. Then he can be extradited to the US. Sweden can relax - he's a convicted sex offender now, extradited from the UK. It's harder for him to get legal support in Sweden - he's English-speaking, as are the majority of his supporters.
And the US gets their man. No government wants some renegade out there leaking their secrets.
The UK and US will obviously have discussed his extradition. They've agreed to try the Swedish route first. It doesn't have a political cost for the UK government.
Assange himself pointed out that it is much easier to be extradited to the US from the UK (which extradites to the US almost anyone for pretty much any reason) than from Sweden (that as far as i know very rarely if ever extradites to the US).
If he was really afraid of being extradited to the US, he would want to be in Sweden rather than in the UK.