And so, all we know so far is:
-Release date: March 24th
-Price: 3600jpy (without tax)
-The design of the artbook will be the same as the 2015 edition of the manga, so that when you put them together they will look like a set.
-There will be a bit more than 100 illustrations all chosen by CLAMP
-There will be new comments about each artwork and Clamp's new insight of their artworks after so many years
-A big poster of 70cm x 100cm with the chronology of CCS will be included with the artbook. No idea how the end product is supposed to be?
-There is also going to be a "Glitter foil clear case" is (キラキラ箔押しクリアケース), literally a transparent plastic case with glitters ^^; And that certainly reminded me of the limited edition of volume 09 of CCS, which came in a transparent sleeve with an illustration of Sakura on it. The sleeve contained both the manga and the 12 postcards that came as a bonus. In this case, it will contain the artbook and the poster.
Also, they confirmed that there is going to be a new manga of Card Captor Sakura:
It is not determiined yet when the chapter will be released. And they are asking us to be patient and wait for them to post more information about the upcoming manga.