Yikes! From the 5.40 relese notes:
· MPLAB X IDE now a 64-bit application only. This version cannot be run on 32-bit operating systems; 64-bit operating systems are required.
· MPASM no longer included in install. MPASM toolchain is 32-bit and is no longer supported. Therefore, you will see a message on opening the IDE that there is no toolchain installed.
This does not sound too promising for the future of our beloved compiler...or does it? Perhaps this will allow (or even push) MeLabs to make the needed changes (though, as much I hate to say it, I personally doubt it).

tumbleweed says that the new assembler isn't compatible with MPASM, I'd like some more details on that, like have they completely changed it so it will no longer be able to assemble a target executable from the .lst file PBP produces?