I would love for MH4 to go to Vita and have local/online cross-play with 3DS owners. If I cared about hardware sales and killer apps, the window for Vita to surpass 3DS was closed a long, long time ago. So even from a Ninthing perspective, there's no reason for Vita owners to be deprived anymore.
yeah, in terms of maximum inflictable damage MH4 has already done that - 2.x million first week sales and a rabid hunt by fans to find more copies / 3DSs
If a Vita MH does come, it'll be a branch with significant differences (apparently Sony still have claims on MH Portable) - not huge wholesale new stuff, but enough to make them different (like MH3G and MH3rd) - because that way rabid MH fans will buy it. Though as per MH3rd to MH3G, i'd pass simply because if it's just more of the same stuff then i'm not prepared to reinvest XXX hours repeating from scratch.
I am surprised that Capcom haven't started a "MoHan Cloud" service where you can upload your save data to so that they have the option of allowing version switching though i'd assume platform holders would be wise to that!
Also at this point i don't think Capcom would put that much effort into improving MH for Vita - they'd maybe outsource it to Xing again and they'd tidy it up a bit but.... yeah... that's about it. Maybe use some MH4U assets? It's not a big enough jump - at this point I want MH that looks like Deep Down and we aren't ever getting that
and basically now MH4 is here and it's hot hot hot then yeah... who cares? I was wrong and moaning about MH (again) - they knocked it out the park so far and i hear the game difficulty ramps up nicely post HR4.