I really think NISA should fast-track a Disgaea 5 port and forget about releasing them in order.
It was fair enough releasing the first one, but to then wait a year only to release Disgaea 2 seems like a load of wasted effort. At the rate they are going, by the time they get round to D5 (or whatever is the most current version) it'll be old hat by then.
I don't know about 5, it's already old hat right now.
But if they are smart, Disgaea 6 (or whatever else comes next) should be day and date.
And then pad their schedule with an older port every 6 months or something when there's nothing new to release.