Depends on the region you are in. Japan currently have a Jirachi event, it's possible that will be the next Worldwide one.
(Information correct as 7/7)
regigas
On march fourth in pokemon black and white 2.
don't know. They don't tell you about future gifts. they tell u when they are giving our out. btw: its mystery gift not mastery gift
The next Mystery Gift for Pokemon Soul Silver will be Celebi (Serbii). Starting March 6, 2011.
some time after Pokemon black and white comes out in spring 2011 march 6
the best pokemon in black and white is victini you can catch him if you go on mystery gift after you get the victini card you can pick him up from the mail man next to the door at any pokemon center
it is on June 14 2008
it would probably be this year
acures i think im not sure
As of Oct. 15 the next mystery Gift will not arrive for about 3-4 months, when the next Pokemon movie is premiered. You must take your DS to the theater and set it on something Like "Find Mystery Gift Via Wireless".
type in bulbapedia on google
Just have a friend then wait and it will tell you the next step.