As I said in another thread, here is how things will go over the next several months:
Japan just got AA today. We will be getting SV on August 19th. (Not 18th, like WPM said.) We all knew that.
In October, Japan will be getting HGSS themed set. Meanwhile, in early November (Most likely November 4th) we will be getting the AoA set, minus the Arceus cards. This will give us a tiny set, of about 98 cards. This number might be slightly higher if cards in the theme decks get reprinted. (Main set reprints most likely will get reprinted in the U.S release.)
At the end of the year, another set will be coming out in Japan, likely to be a second HGSS set. (Platinum had 4, DP had 7...only 1 HGSS? I don't think so.) Then, in February 2010, (likely February 10th.) will be getting HGSS1 with the Arceus cards from the AoA set. We will know how big the set will be when it comes in Japan.
Finally, in May 2010, (count on May 19th.) we will be getting the second HGSS set, while Japan gets two more sets in March 2010 and July 2010. The July set will be based on the 13th movie, which will likely be around Ho-oh and Lugia.
I'd quote this "predicition" if it turns out right in a year from now...if it wasn't so big.