I give it a couple of weeks before screen shot of "violent" groups on Signal go viral, and the ban hammer will come unless they build a backdoor or remove the end-to-end encryption feature entirely.
M'y guess is Moxie would shut the company down before introducing a backdoor.
Also, if the gov tries to ban it, its just open-soirce software, right? Haven't courts (in the US at least) ruled that code is speech, and therefore protected from government restrictions by the 1st Amendment?
Except I doubt that's how it will work. They just have to get Apple and Google to bow to the pressure again and remove it from the app store. Restricting the first amendment is a lot easier if you can effectively do it without actually doing it officially.