As previously targeted, it is confirmed lately that the 645D is to be on sales on May 20:-
http://dc.watch.impress.co.jp/docs/news/20100427_364095.html
(in Japanese)
Also, the new kit lens DFA 645 55mm/2.8 AL[IF] SDM AW (Umm.. What a Loooong Name!) will be delivered at the same time.
And, the latest pre-order street prices at Japan can be as "low" as JPY 763,200 (roughly equals to US$ 8,200):-
http://kakaku.com/item/K0000095422/
(in Japanese)
It seems that the availability is good.
Previous News:-
645D Will be Shipped within Two Months