Arduino has released two entries of its wiki about the specifications for 1.5:

• Arduino IDE 1.5 3rd party Hardware specification
• Arduino IDE 1.5: Library specification

I like the new structure described in 3rd party Hardware specification. It is cleaner and more open to 3rd party. I've already implemented it in my embedXcode project. 

Now, IMHO, I'm not a big fan of the new library specification, as the files of a single library are going to be split among different folders.

See the example provided for Servo: 

• Servo.h goes under Servo/src/ 
• but Servo.cpp is under Servo/arch/avr/.

This means parsing the directories in search for all the files and thus makes the makefiles more complex.

What do you think?

As Arduino is taking the lead over Wiring, I guess all the Processing-based Wiring-derived Arduino-like IDEs have little choice but to comply with the new standard. 

I hope Arduino is considering taking a more advanced editor with now standard features as code completion, syntax helper, and a much needed debugger.