The magic box already had a story on this. A game magazine in Hong Kong had an article on Monster Hunter Portable 3G coming december 2012. However it is apparently actually for the PSP and just has some extra features on the PS Vita. So by the sounds of it won't feature all the graphical improvements you might expect of a vita game.
http://www.the-magicbox.com/1201/game120125d.shtml
If the rumour is true it should cause a reasonable rise in PS Vita sales. At the same time it will be the third version of Monster Hunter Tri to exist. Kinda hard to judge how many people will buy it after it has been available for Wii and 3DS for so long. Not to mention if it's also on PSP then it's difficult to say if people would buy a new system for a slightly upgraded version.







