True - I'd forgotten that part.
In any case - the case was reopened in November 2010, and Assange didn't enter the embassy until June 2012. If this truly was some sort of grand conspiracy to get him extradited to the US, I'd imagine the CIA has more reliable and straightforward methods of arresting/disappearing someone.
In addition to the above, EU law forbids extradition chains (Assange extradited from the UK -> Sweden, and then Sweden -> US) without explicit permissions from all involved countries.