Dark_AleX has updated his blog in regards to all the questions he is receiving about 4.00 M33 custom firmware. Rather than rephrase it, here’s what Dark_AleX has to say about 4.00 M33:
Just a little update. Watching how many people were asking for 4.00m33, it’s interesting to make somethings clear.
Due to the lack of updates [...]

Good news for those that are awaiting for news on 4.00 M33. Mathieulh has commented on a couple of great new features that are going to be introduced in this up and coming M33 custom firmware.
Custom Firmware 4.00 M33 will feature an XMB recovery mode, which will allow access to the recovery menu from [...]

Judging from the comments made on PSPGen (The GEN/Miriam Custom Firmware homepage) Version 4.00 GEN might not see the light of day as a public release. Although a beta version of 4.00 Gen has been completed by Miriam, Team GEN might keep this release internal as they are aware that Dark_AleX and team M33 [...]

Team M33 have returned and are busy working on PSP Custom Firmware 4.00 M33. The master himself Dark_AleX is working on this now. Its also reported that there will be a brand new recovery menu in 4.00 M33, no other new features to be added at this stage other than what was included in the [...]