A few hours ago, another CoroCoro picture showed up on the Japanese forums. This one involves Jirachi. A special distribution of Jirachi is to begin on June 19th. It is at Level 5 and is said to have special attacks. It also unlocks a new area in Heart Gold & Soul Silver when traded over. The method of distribution is as of yet unknown but as soon as we are sure, we'll let you know
Edit: It appears, from a clearer scan, that the Jirachi may be given over Mystery Gift over WiFi Connection in Japan from June 19th to July 17th. However, as this is not confirmed, and could be in relation to its release at a special McDonalds, confirmation of this, as well as what game it will be using should be forthcoming.