The Swedish rape allegations were an obvious sham and have already been dropped years ago. Usually when this happens the case is just dropped, yet the UK really pressed in arresting Assange for "failing to appear in court", which is most countries is a minor thing (the accused is not punished for lying in court or missing court dates). I think it's obvious that any excuse will do for extraditing him to the US, to make an example of him. But so much time has passed and the case is so public now that I at least hope the UK will save face and free him instead of extraditing him.
They dropped the investigation and the arrest warrant, not the charges. The investigation can still be reopened and he can still be questioned and charged if he returns to Sweden before the statutes of limitations run out.
It's extra interesting now because the US is now led by a government that is alleged to have illegal foreign help during the election campaign, notably through Wikileaks. I don't think the current president would want Assange extradited.
The statute of limitations has run out on some of the minor charges, but not the more serious one. While Sweden has closed the case and dropped the international arrest warrant, if he returns to Sweden before August 2020 he can still be questioned and charged on the remaining allegation.