...if they aren't working on patches why should they rejig the engine?
I don't like that they abandoned bug fixing either, but given the way EA are tightwads, and devs are crying about piracy these days, not to mention that CryTek has never been all that great at bug fixing, it's not all that surprising. Anyone that's played Far Cry a lot knows there are still some major bugs unfixed, like the infamous "Cooler" bug where the apes don't spawn at the end of that level sometimes, causing you to have to play the whole level over, and the repeating assault rifle sound that often occurs when you kill a merc carrying one.
Come on people, this is CryTek, they aren't long time game devs like Valve, Id, etc. They originally intended Far Cry to be just a dino graphics demo, not a game. They sort of fell into gaming by accident. Just because they can make brilliant environments doesn't mean they are going to release bug free games.
Oh, and why "should" they rejig the engine? You mean why
did they. Warhead is stand alone because of it. It's already been done, but that doesn't mean translating those optimizations into a patch for Crysis will be easy. To be honest I don't even know if CryTek is happy with their Warhead sales figures.
At least for now there's Far Cry 2 we can play. It's not a bad game, but the AI, though brilliant at times, is very arcadish and laughable at others. It is a truly unique game and experience though. FC 2 and L4D may stand out as the most original titles of their time for a while to come.