An online beta will start sometime in May, and according to the website it will have a release date of summer 2010. If your wondering if there is a western release date, there is none at this time. Capcom is hoping that Monster Hunter Tri for Wii does better, then they might port this over to the western gamers. I wouldn't hold your breath though. Also for those that don't know Monster Hunter Tri will be released as a bundle in April with a non-motion control pad, that looks suspiciously similar to the PlayStation controller.
I say Japan can keep the franchise honestly. Capcom seems to think that if they continually shoves this game and it's multiple inceptions down players throats it will become this great success in America. As seen in the last releases (anyone remember the PSP's Monster Hunter Freedom?) it's obviously not working. Let it go. The small portion of gamers that actually enjoy this have either imported the games or they are not a large enough market in the US to continue developing it here.
I agree that this style of game works well in Japan and Asia. It's just one of those games that cannot survive out in the West. I also understand that Monster Hunter is one of the best selling PSP games in Japan, but turning it into an MMO and slapping a monthly fee on something that has been free for such a long times seems like a silly move to me. Unfortunately the titles which will be on XBox and currently on PC will not run on the same servers, just to add insult to injury. Personally I think this was a big waste of an announcement. If they bring it state-side I wish Capcom the best of luck, because with all the new MMO's being released in the next two years, I really think this game could fall to the wayside.