There will never be another one again, unless it's over wifi.
So far, there is no Nintendo event to get Arceus for your DS or DSi.
in 2010
It is from an Nintendo Event.
No further events have been announced by Nintendo as of yet.
In Japan in December 2010
there was none that i know of...
Official events are the only way to catch Arceus.
You have to attend a official Nintendo event. For now Arceus has been released only in Japan.
Nope.
you need the action replay or a Nintendo event.
Yes, but you have to get it from a Nintendo event (If they have any new events for Arceus) or trade with someone who got it from an older event.
There has been no next events for Arceus announced for 2010.