Increasing key length has been the main way to protect crypto from Moore's law. That law is somewhat predictable: we can now how much time a key can hold depending on ressources needed to crack it.

The real problem here: cryptanalysis advances like Joux's tend to create big leaps, much bigger than what we predict based on Moore's law.

And there's the problem that RSA 2048 is slow, and RSA 4096 is so slow that it's impractical...