Firmware 3.50 was decrypted shortly after release, but not fully since Sony implemented various changes in the PRX formats. After being quiet for some time, new updates regarding the decryption progress as well as that of the next custom firmware have emerged. Accordingly, Mathieulh and Dark AleX are indeed working on Custom Firmware 3.50 OE and the project is already 5 per cent complete.
There are no details of what the new custom firmware will offer, but one of the main reasons for the new firmware is to utilize the 3.50 kernel. Lets hope the pair include some interesting new additions to the firmware. Look out for more details soon.