Too difficult to get the PS4 version running on Vita (especially due to the PS Vita not supporting unreal engine 4) and 3DS version wouldn't really work on anything else due to the game being too specific for that hardware. A PS Vita version would of ended up having to be built from ground up on it's own engine seprate from the PS4's and 3DS.

oh dang! Sucks for Sony and Vita users! That could have re ignite its sales. 

I figured as much, considering they likely started on the Switch version at a much later date. Hopefully that version will still do well.

Now it seems thé Switch version wont éven release before 2018, they updated thé 2017 date to TBA on their site

If switch doesn't get DQ11 in japan this year then I see no point releasing it at all.