Looking at the album releases for May on fan-net. I believe they should release her album on the 27th. There isn't any competition on that date. All based on their Oricon page.
Meg reached #8 with her album that was release in June 2008 but it sold WAY less than WISH did in it's first week. See:
http://www.oricon.co.jp/search/resul...=8&submit5.y=3
May J. is a Sony artist so that's why I'm thinking they won't release it on this day. But I doubt Sony works. May J.'s last album which was released in 2007 was at #50. See:
http://www.oricon.co.jp/music/release/d/738002/1/
Ｍｉｓａｋｏ Ｓａｋａｚｕｍｅ is on Koda's label but she isn't a good seller.
Mayo Okamoto her last album released October #100. See:
http://www.oricon.co.jp/music/release/d/781672/1/
And finally Sotte Bossa his last album, November last year #40. See:
http://www.oricon.co.jp/music/release/d/789246/1/
This was RUSHED in the fasted way cuz I have to leave so I hope it makes sense.
Take a look for yourselves and say which dates you'd prefer. May 27th right?
http://www8.plala.or.jp/fan-net/NewSong/200905sale.html
(On a somewhat not relevant note. May J. should leave Sony because she has a new album coming out next month and not one single was released.
EDIT:She did leave Sony. Her new album FAMILY is being under Rhythm Zone same as Ｍｉｓａｋｏ Ｓａｋａｚｕｍｅ)