There was some small scale experiments, to have a fully working industrial prototype, the amount of problem to solve is just colossal. I think 40+ years is a much more reasonable guess. The thing is we don't even have a realistic timeline for those, because even that requires more research.
We need way more data to say something about LFTR.
Fusion on the other hand has an estimate timeline. If everything goes well with ITER, DEMO should be operational around 2040-2050+. And actual power plants will use DEMO design.
That's what we know today. With more research, we could find better design and faster ways to get fusion (Wendelstein 7-X) or we can find more trouble along the way.
