The problem is that Perlmonks does not run on the stock Everything engine. The code is heavilly modified. Upgrading to a newer version of Everything would mean porting those modificatons to it as well.
The newer Everything engine is also slower. So that wouldn't be a great trade-off. There is much talk/work about making it faster, but, as I understand things, it is still likely to be slower than what we are using (and, AFAIK, its node cache is still broken in the same ways).