This may seem negative to people here but this is simply my prediction on how the scaling drama is ultimately going to unfold.
1) UASF does not have critical mass, nor 51% of miner support required for it to be safe, and will not gain it in time to activate the existing Segwit deployment. Prominent members of Core arguing for caution have shut down momentum around it.
2) The absence of UASF will guarantee that the current Segwit deployment will not achieve the necessary 95% activation requirement and will fail.
3) Additionally, after failing a 3rd attempt (XT, Classic, BU) at hardforking the blocksize, the "big blocks" camp will finally rally around a softfork like the current (or a modified) extension blocks proposal. This proposal will fix malleability and support segwit, while providing some mechanism for clients to support larger blocks and remaining (somewhat) backwards compatible.
4) Mining support for this new comprehensive soft fork will easily surpass 50% and likely 75% as miners will be able to support it while saving face.
5) Because it is a softfork, it will be unlikely that opposed parties will be able to gather enough opposition to prevent it from being enacted. My understanding is that a softfork with 51% support is effectively safe.
6) The industry will scramble to support the new softfork as extention blocks do make for a more confusing user interface.
To be clear I am a Segwit supporter and I think it would be the best solution at this time. But, I think todays announcement of Bitpay and Bitmain's partnership makes it likely that this is ultimately going to happen. In the end the small block camp will get segwit and transaction malleability fixes, while not hardforking the network, and the big block camp will get the ability to increase the number of onchain transactions for some number of clients supporting them. What this does to decentralization ultimately im not sure, but presumably core nodes can continue in an intelligent way with opt in support for extension block transactions.
Again, this is not necessarily what I want to happen. This is what I think is actually GOING to happen. Please tell me why I'm wrong.