Dmitry is the man who originally wrote eaccelerator, Zend caught wind of him and hired him! Then he worked on opcache and has done some amazing things in getting the Zend Engine and PHP itself flying. He's a very smart cookie.
His good sense is obvious by the way he stopped going down the JIT route and zeroed in on the bigger performance drain, memory allocation, instead. The smart programmer knows how to write a JIT; the wise programmer knows how to not write a JIT.
JIT is probably coming too, just with current way the engine built it turns out it is very hard to do JIT that makes any real-life impact. One can get magnificent benchmarks, but once you hit real-life apps, you get very low improvement. Thus a more attainable goal was chosen, but JIT may come back yet.
