There’s currently no information about any big additions to the HD remake, but we got the official Japanese title as Makai Senki Disgaea Refine. It is also mentioned that the HD remake will see not only improvements in graphics but also playability.
A limited edition version will go for 9,200 yen, and it includes the original soundtrack and calendar, all in a special box.
Disgaea: Hour of Darkness Refine releases in Japan on July 26, 2018. Its platform(s) still remain unknown.