Stuart, CD Japan publish his calendar always later than HMV Japan.

This is the link to the prereleases page: http://www.hmv.co.jp/fl/4/5/1/

In fact right now the HMV page is missing the old and live Deep Purple albums scheduled for july, and CD Japan too. So another source that I check time to time is http://www.mediawars.ne.jp/~mundo/cdjapan/link.html to see if something is missing in the other places. Check July to see all the D Purple albums for july 23. In fact HMV have them in his shop but I don´t know why not in the prereleases area: http://www.hmv.co.jp/search/index.asp?formattype=2&category=1&keyword=Deep+Purple&target=MUSIC

Also to know what releases will have promo box from Disk Union you can subscribe to the kamijacket newsletter in the DU page and translate the content using google translator form japanese to english or any other language. This is a very valuable tool to not buy as individual albums what you will like to have boxed.

This is the link:
https://mail.diskunion.net/mail/single.cgi?genre=kamijack

Only need to write your email adress, then you will receive
a message with another link to give your confirmation. So insert your email adress and press the button, in the second pop up window press the left button and you will start receiving the next newsletter.

Cheers

Domingo

PS. I use CD Japan more to check old releases than for future ones. Sometimes using the calendar mode and others searching by band or album name. For that CD Japan offers advantages because they don´t delete the OOP albums so you can now what albums were included in each release.