Without any official announcement, apparently Nintendo has shipped new backlit Game Boy Advanced SPs to some retail stores. Previous Game Boy Advanced SPs were front lit.
The new backlit model, AGS-101, is available in Graphite and Pearl Blue colors.
Its been theorized that Nintendo didn’t issue an announcement such as to not over shadow the already released (September 19th) Game Boy Micro, which is also back lit. The Game Boy Micro is the smallest of the breeds at just .7 inches deep and 4 inches wide.