Trevor Bedford had a tweet that indicated a 25% reduction in social contacts results in a 50% reduction in cases after 1 month:

https://twitter.com/trvrb/status/1237934525281259521

I think it's very likely that Wuhan or Italy style lockdowns will bring r0 under 1, based on the experience in Wuhan and Italy. That means the disease eventually dies out. Because it's endemic elsewhere in the world, it'll eventually be reintroduced and we get multiple waves, until eventually enough people have had it to generate herd immunity. But each wave starts back at the "containment" phase, with contact tracing and individual isolation, so combining lockdown + those measures + travel restrictions could probably buy enough time for a vaccine.