I'm not sure how many there will be. It can be hard to tell with gaiden. It started in December of '09 in Monthly Young Magazine, but the last release date I can find is January, so it might be over.
According to this
news post on ANN, Takada-sensei had just finished up a series, so this might have just been something to pass the time until he finishes preliminary work on a new series, or a way for the magazine to increase its readership by starting out with a side story to a popular manga, even if it is oldish. Seinen magazines have an older reader base anyway, so they'd be likely to remember stuff from a longer time ago than kids would anyway.