The following comes from Nippon Ichi Software president Sohei Niikawa...
- the difficulty of porting from PS4 to Switch varies depending on how each studio approaches development
- the porting process was relatively smooth for Disgaea
- there was nothing NIS had to downgrade
- even in portable mode, the experience still remains same as PS4 version
- Disgaea 5 was chosen for Switch because it would be smooth to port
- NIS also thought it would be better to release its key product
- NIS received many requests to port it to Vita, but if this happened, it would have been necessary to downgrade the game
- NIS brought the game to Switch as a way of fulfilling the fan request for a portable version of Disgaea 5
- NIS says they are definitely making more Switch games
- They will not be making just one game and calling it quits
Lots of interesting tidbits
Summary curtesy of gonintendo. http://gonintendo.com/stories/272446-nis-explains-why-disgaea-5-is-coming-to-switch-no-downgrades-fi