YOSHIKI announced it during his YOSHIKI Classical concert in San Francisco on April 28, 2014. Immediately the banner went up, in a section of Yoshiki’s homepage: http://www.yoshiki.net/xjapaninfo
The X JAPAN homepage http://www.xjapanmusic.com>was updated during the night. The Dragon wrapped around the X is gone, and it now shows the banner with links to the member’s pages (if they exist).
A few hours after the announcement, SUGIZO (who had been “special guest” at the opening of the YOSHIKI Classical World Tour) tweeted about it, in Japanese and English:
[X JAPAN] 2014年10月11日(土)MADISON SQUARE GARDEN (ニューヨーク、USA)にてライヴコンサート決定!その他の詳細は決定次第お知らせいたします。 http://t.co/3yI5BB7J42 pic.twitter.com/RKdBH4AfF8
— SUGIZO (@SUGIZOofficial) April 30, 2014
[X JAPAN] X JAPAN performs at MADISON SQUARE GARDEN (NY, USA) on 10/11(Sat). http://t.co/3yI5BB7J42 pic.twitter.com/KOSpMYvO8N
— SUGIZO (@SUGIZOofficial) April 30, 2014
His webpage http://sugizo.com/ also shows the news today.
ETA 1 May: Yoshiki’s announcement on Facebook
ToshI’s page still does not have any news.