Reportedly, the first will have a qHD (540x960) display, while the second and third will have 720p displays. Furthemore, a XML file on Samsung Mobile's website seemingly confirms the SM-A500 as a 720p device. As you probably guessed it, these smartphones will share continue the Galaxy Alpha's design language, which, at the very least, suggests Samsung is ready to embrace aluminium and other metals as an everyday build material.
Another bit of information suggests that the A-series phones will have higher resolution front-facing cameras. It's not known how many megapixels Samsung will hit, although the Galaxy Note 4 is suggested to have a 3.7MP selfie snapper, so there's that for a clue.
Allegedly, the new devices will be introduced sometime in September, although we wouldn't bet for an IFA 2014 announcement, considering the Galaxy Note 4 will be the pinnacle of the event.