More than a few have been somewhat confused by Google's Android and media rebranding efforts around the Google Play name. But it looks like it's here to stay, and if an Audiobooks portal spotted by Google Operating System is any indication, they're looking to expand. Of course audiobooks are a natural extension of both Google Book and Google Music (now Google Play Books and Google Play Music - see how that works?) but they may also be looking into magazines, catalogs, newspapers and other periodicals.
This speculation comes from a previously discovered list of website domains registered to Google, which include "googleplaymagazines.com", "googleplaynewspapers.com", "googleplaynewsstand.com", "magazinesonplay.com" and "newspapersonplay.com". At the time the websites were taken to indicate that the much-rumored Nexus Tablet might be labelled "Google Play". While that still might be the case, it's an unofficial confirmation that Google is at least thinking about periodicals as well.
There's no indication that audiobooks and periodicals are heading to Play immediately, though there are plenty of alternatives already available (and a few independent audiobooks already posted to Google Music). Google may just be preparing for their introduction months or years from now, as each new section would require negotiation and licensing deals with dozens of publishers. If these features were on the horizon in, say, the next couple of weeks, Google probably would have just waited and included it in a slightly later rollout.