They said they wanted to do a PS4 game because they hadn't done a major traditional console entry since 8, and obviously PS4 is the clear choice for that.
As for the West, it seems no more or less Western focused than 8. Everything about it seems quite similar really.
They want it to sell, and they want DQ to be a powerful brand in the West, certainly, part of that should be making it available to more platforms. I don't see why it's not on XBO too, it should be. But the actual process of producing a PC version of an x86 PS4 game on UE4 seems like it would be extremely painfree. Games are built on PC anyway, the engine is already on there, and beastly at that. They knew it'd take about a year for localisation, and the PC version considerably less time than that. Seems like a no brainer, and I'm extremely pleased to see it happen, even though I'll be getting it on PS4.