If enough of the community members who want to see Segwit activate on Bitcoin support BIP 148 – Bitcoin will get Segwit with activation beginning in August. (that's this year, not next year or the year after).
I won't try and force you into it but instead would like to point out a few things that might help you decide to support a UASF if you are currently undecided…
85% of nodes support SegWit.
86% of businesses support or are prepared for SegWit.
Miners would have to follow if all the above signalled support for BIP 148.
Support is well underway with over 10% of nodes already support for BIP 148.
Changes in Bitcoin need to occur in order for the technology to evolve. So changes need to happen somehow. I would like to think that the Peers in bitcoins Peer-to-Peer decentralised network are the ones who should approve and activate those changes.
Changes are suggested by developers when they release new versions of the reference client.
These changes are adopted by users and the business community if they like them by running the new code.
This is what happened with the current Segwit deployment – developers made a change, the majority of the community said 'yes' to it and have been running that code since version 0.13.1. of the Core reference implementation.
BIP 9's activation method (the one that Segwit uses) was intended to make sure that miners had upgraded to a community accepted change in time for activation to avoid network disruption on activation. It requires 95% of miners to signal acceptance. Because of this approach it only takes just 6% of miners to overrule the choices made by majority of Bitcoin's community. (see a co-author's own recent comments on BIP 9's flaws here for reference)
Change needs to come from somewhere and I'd rather it was users and the wider community that got to decide those changes over a small number of financially motivated miners.
There are many reasons why miners might oppose Segwit; the continued use of ASICBoost and the current rewards they get from high fees are just a couple of possible reasons. The reasons don't matter as much as the fact that a small number of them can over-rule changes that are supported by majority of the community.
Whereas some people try to garner support by trying to make people fear the consequences of supporting a UASF I would look to highlight the positives in supporting it. Same end goal in mind – just different approaches to getting there.
Just to repeat:
If enough of the community members who want to see Segwit activate on Bitcoin support BIP 148 – Bitcoin will get Segwit with activation beginning in August.
Some useful resources to help you signal your support: