So in this coming Fall, PSP’s will be able to access the PS Store directly from their PSP, similar to that of how PS3 users are streamed the store as well.
Not only that though, new ad-hoc feature:
This Fall, select PSP titles will allow players to go through the PS3 to take their ad-hoc multiplayer modes online. When playing in this fashion, the PS3 can be used for text and chat messaging and also for matching.
Monster Hunter Portable 2nd G is confirmed to be compatible with this and that it will work with all PSP models, sounds like a very enticing addition!