Disponibile a breve la 1.5.4 che supporterà la YUN
Alongside the new board, we are also releasing the new Arduino IDE Version 1.5.4 (available in the next hours for download) featuring support for Arduino Yún, some new features, and general bug fixes. The new features include:
Board recognition: every time you connect an Arduino board, the IDE recognizes the type of board you are working with
Memory: when you upload a sketch, the IDE tells you how much memory you are using
Copy Error button: you can more easily copy and paste errors to share them in the forum
Interessante il nuovo sistema di riconoscimento automagico della board. 
revision.txt temporaneo:
ARDUINO 1.5.4 BETA[ide]
- Revert to English locale if the system default is not available
[libraries]
- sam: fixed wrong SPI initialization (noblepepper)
- updated all instances of Adafruit_GFX to the latest version
[core]
- avr: fixed bug introduced with recent optimizations in HardwareSerial (atmega8 cpu) (darryl)