Every Ys gets translated, the question is WHEN. Ys origins been out for awhile and we just got it here. And Ys I & II and Ys III (Oath in Felghana) were remade and released here. Getting it over here is a high possibility, but I wouldn't hold my breath on it being released any time soon, Falcom is one of the companies that actually cares to translate a game properly and not just port over a japanese game with Engrish.
Falcom doesn't do the localizations themselves though, it's XSEED that's translated all the recent games. Well, they've worked with the fan translators for Chronicles, Oath, Origin but it's still them and not Falcom. It's to everyones benefit that XSEED cares and wants to give these games the localizations they deserve.
And yes, the odds are good that they'll add this game to the list eventually. One of XSEED's localization ninjas is a huge fan of Ys IV and his reaction to the announcement of the remake was memorable.
I wouldn't be so sure of that. The series has some recognition value now (that flash sale that shot Ys Origin up the charts on Steam looks like it's helped a ton) and the extra exposure gained from physical distribution is likely to offset the increased costs by a good margin. This game has the advantage of not being an extremely niche title nearly impossible to market (Corpse Party) or impossible to get into stores because the genre is DoA (the PC Ys games) and being on one of the current generation of consoles helps too.
And precisely what logic led you to that conclusion? Was it the fact that the Vita is a major console which XSEED has released games for in the past? Was it the fact that this game uses Vita touchscreen/pad functionality such that a PC port isn't a plug and play process? Was it the fact that Falcom doesn't currently have a PC division and XSEED lacks the programmers to port a game? Tell me, oh all-knowing one.