I would say the next country is likely much sooner than 2050, because 24 years is longer than the timelines for China, for India and Pakistan given when they became independent even assuming they started on that immediately, I think for Israel but it's hard to be sure given the secrecy, South Africa arguably but IIRC they didn't complete it, and obviously the USSR, USA, France, and the UK.

Yep at the end of the day, this is 1940s/50s technology. It's complicated but not that complicated