While a release outside of Japan has yet to be announced for Monster Hunter 4, a new feature that generates random quests has been detailed. These quests will also increase in difficulty and rewards the more they are replayed.
This feature can be used in the Unknown Forest and will become a Guild Quest if successfully completed. Once it becomes a Guild Quest, players can share the quest via Street Pass as well as play it on multiplayer. However, only ten of these quests can be kept at a time.
As stated earlier, replaying these quests makes them more difficult and rewarding. One of these rewards is the exclusive "Excavation Equipment." Hunters may also find themselves fighting monsters that cannot be encountered by normal means.
For now, Monster Hunter 4 will be released exclusively for Japan on September 14th for the Nintendo 3DS.
Source: Operation Rainfall