Not a chance
He's stuck, and it's a situation of his own making. Failing to answer bail might get him 12 months in the slammer. If they consider him to be in contempt of court, that might be 2 years. Either way he's practically guaranteed a custodial sentence, and every day that's passed since has made that even more certain.
If there's one thing a British judge really, really hates it is a defendent taking the piss, especially to this extent.
I wonder if there's a certain amount of pride in play here. If he leaves the embassy and ends up in either a UK (highly likely) or Swedish (arguably less probable) jail and the US fails to show any interest whatsoever in seeking his extradition (practically guaranteed), he is going to look a bit silly...