Effect of $L_n[1/4,c]$ integer factorization on RSA-2048
Unfortunately, deriving actual numbers from asymptotic bounds makes little sense (after all, $10^{36}$ and $10^{23}$ are both $O(1)$). Getting an idea of the actual cost of running an algorithm requires a fine analysis of the algorithm itself; asymptotic results are not sufficient. An $L_n[1/4]$ algorithm for factoring would be a great theoretical result, but it wouldn't necessarily perform better than the current algorithms on, say, RSA-2048.

Fear the hidden constant factors.