According to the article, not that likely:
Terms requiring users to sue in specific courts are usually enforceable, Vanderbilt Law School Professor Brian Fitzpatrick told Ars today. "There might be an argument that there was no consent to the new terms, but if you have to click on something at some point acknowledging you read the new terms, consent will probably be found," he told us in an email.
A user attempting to sue X in a different state or district probably wouldn't get very far. "If a suit was filed in the wrong court, it would be dismissed (if filed in state court) or transferred (if filed in federal court)," Fitzpatrick said.
They seem to be mostly upset about Apple requiring browsers on iOS to use Webkit instead of implementing their own backend. Which is yet another problem the UK wouldn't have if they'd stayed in the EU, where that's already been dealt with under the DMA.