I'm not going to pass judgement on Assange although I am inclined to believe that he has been set up by the Americans and that the timing of the sexual assault claims in Sweden is too suspicious to be coincidental. However, it is important to bear in mind that Sweden is a member of the EU and signatory to the EU Arrest Warrant. It is because of an EU Arrest Warrant that Assange faces extradition to Sweden and it is because of the EU Arrest Warrant that he would be foolish to surrender himself to the Swedes no matter what promises they give him about not shipping him off to the US.
The EU Arrest Warrant is little more than a technicality, a procedural mechanism for the legalised kidnap of one country's citizens on the basis of an accusation by the police force of another country without the need for any evidence to be presented. For an EU Arrest Warrant to be considered valid it simply has to have all the relevant boxes filled in and a signature, whether there is any evidence of the crime the subject of the warrant is accused of even being committed, let alone by the accused, isn't a consideration. Grounds for objection to an EU Arrest Warrant are pretty much restricted to whether the form has been filled out correctly and whether the correct procedures have been followed.
It is for this reason that Assange would be very silly indeed to surrender himself to Sweden even if they promise not to deport him once he's there. Once in Sweden, if charges are dropped against him or he is found innocent then all it takes is for a US lap dog such as the British government to issue an EU Arrest Warrant themselves and the Swedish government would be obliged to hand him over. If the Swedish government is conspiring with the UK and US to get Assange to America then this is almost certainly what will happen.