either way whether it leads to him being sent to the USA or him being allowed to remain here.
I think the chance of the US not getting their way here is close to 0%. It's a show trial. The US has suffered reputational damage at his hands, and they will want to make an example of him. It was perhaps a little foolish of him to enter a country that is on favourable terms with the US. Contrast Assange's movements with those of Edward Snowden.
The family of Harry Dunn and various parts of the media in the UK are against extraditing Assange simply on the basis of what many are calling a one-sided extradition treaty
Any interaction between the US and the UK will be one-sided, be it an extradition treaty or a trade deal. This is inevitable given the disparities in power and influence between the two countries. The US is a global superpower. The UK is not. Simply, the UK does as it is told.
If we look at the 'Special Relationship' that exists between the two countries, then the US benefits as the UK is in a strategically important location as the gateway to Europe, in both trade and defence, and the UK is also useful as a military ally so that any US adventurism in say the middle-east seems a tiny bit less unilateral. As for how the UK benefits, well, that's a little more difficult to determine. Perhaps we are first in the queue for any scraps that fall from the US table, perhaps not. This is one reason why Brexit was a bad idea. The UK outside Europe is stripped of much of its negotiating power, and absolutely at the mercy of US interests.