Around the time Ketsui was released, M2 were asked about Ibara, and they said someone on their team worked on Ibara and didn't want to revisit it so soon, so they went with Ketsui instead. Hopefully they will port it in the next year or two. But who knows. So far M2 have only ported one CV1000 game (Futari), and they seem more interested in porting games on the older hardware. New, proper ports of Donpachi and Dodonpachi would be great to have too.
PS2 DOJ is not quite perfect, and does not have BL included, so I can see why they went with a new port. The X360 port is pretty good but the load times, training mode, and interface are poor.