I've searched for this for a while but get nothing...
There are plenty of proofs to irrationality of $e$,$\pi$,$e^{\pi}$. However, I can't find a proof for $\pi^e$. More, when searching for this I got a answer Unknown on this site(in Chinese), which says
目前为止, $\pi^e$ 是否有理还是一个谜。
Whether $\pi^e$ is irrational or not is unknown up to now(2010).
Thus, I just wanna know whether there's progressing these years...