Anyone knows whether the former will replace the latter or whether they will stand side-by-side? And, if the new achievement replaces the old one, will progress remain or will it be wiped out?
I can't cofirm this, but it looks like it will be a whole new achievement. When they replace stuff or chance criteria they usually edit the existing achievement. If this is a replacement however, i highly doubt that it will count the battles you have won so far, since you can't prove you won those with lvl 25 pets.