The members have already posted statements about it, but they're mostly inconsequential--the closest thing to a reason for the disbandment is NOAH's statement that there's a “gap” between his goals and the reality of the band's activities so far.
The band's last live will be held somewhere in Tokyo (東京), but further details are TBA.
A statement like NOAH's would normally imply (in my opinion) that the band isn't making enough money. That said, they just started their second oneman tour, and it runs until April, so it seems a bit early to decide whether it's a “failure” or not... And they'd just finished their first oneman tour, and held a successful oneman at BLITZ--which was filmed, meaning they have a future live DVD to collect some cash with. If I recall correctly, NOAH was also recently talking about trying to tour overseas.
Long story short, that's not the profile of a band who's going to disband soon (and who announces a disbandment 9 months early anyway?).
In my opinion, there are 3 possibilities:
Of course, all of the above is just conjecture. What do you think?