There's little doubt in my mind that this film is intended to serve 2 purposes:
1) Provide some closure to the fans of the original 2 films. What happened to the original Ghostbusters, Janine and Dana (and even Oscar and Louis). Where are they now? What happened to the business of ghostbusting?
2) Set up potential future projects by introducing a younger cast. This is where the fans and Sony's interests align, albeit for different reasons. As fans, we want to see more ghostbusting adventures. For Sony, it's all about making money. Ghostbusters is a well known IP, but Sony has largely mismanaged it. If GB:A does well, then they could create a new cartoon and future films. We get new adventures, and Sony would rake in some money. In my opinion, they really need a new cartoon to take off, similar to RGB. The toys and other merchandise is where Sony could really make their money. The good thing about the cartoon is that there are far less limitations. The universe can be really expanded upon and they can incorporate the original ghostbusters as much or as little as they want.
Years ago, someone named Burning Knight Raven had an idea for a cartoon called Real Ghostbusters: Super. The idea was that after the events of battling Gozer, the RGBs retained certain supernatural abilities of their own. I tried searching for a link to his artwork, but the page is from the early 2000s, and it seems, erased. There is a reference to it on Spook Central - so I know I wasn't imagining it!
EDIT: The Wayback Machine is a beautiful thing:
http://web.archive.org/web/200006052228 ... perrgb.htm