I’ve suspected that might be the case for a while… it’s just too early to say.
As you pointed out, Slimer is clearly back.
We saw stills from the crew’s visit to the firehouse… and someone obviously went to some trouble to retrofit the doors so it’d look like the did back in the '80s. That could be a stylistic touch, but it seemed like a lot of trouble to go to on a tight deadline when continuity wasn’t critical. How many average moviegoers will notice the difference between a roll-up door and the classic hinged barn doors?
We haven’t really seen photos of the cameos. Sure, we’ve seen Ernie stepping out of a hearse. But that doesn’t tell us much. I doubt that was set up as a red herring… but scenes get cut from films all the time. If we saw more pics with Dan as a cabbie and Bill as a bureaucrat, we’d have more to go on.
The hacks gave the studio a chance to screen their ideas and gauge public interest. I’d be surprised if the internet feedback was ignored in it’s entirety. If you have, say, an e-mail account that gets hacked into… you’d probably change your password. Likewise, I suspect Sony would change some of their plan once it was out in the open. They’re in a competitive business, and having the broad details of the film sitting out on the internet for a year in advance wouldn’t help ticket sales.
Finally, having the original crew appear as Ghostbusters in a full length film at their current ages might be a shaky bet for a longterm franchise that turns kids into lifelong customers (look at how lucrative and dependable Star Wars has been). It’d satisfy the older fans, but they likely wouldn’t mint too many new ones. Having the original crew appear in cameo only has clearly proven to be more upsetting than satisfying to the current fanbase. Sony wants to make money. I’ve argued before that the amount of money they’d lose to disgruntles fans is negligible, and I still suspect that’s the case… but they want to turn a tidy profit. reboots these days are in the fanservice department.
If they bring the guys back, limit their screentime and pass the torch, they hit all of the key demos. It’d just make sense to bring them back, and Sony is probably ultra paranoid about leaks after the biggest data breach in Hollywood history. Of course they’d play this sort of thing close to the chest IF they did it.
So… it’s possible there’s a fair amount of misdirection. But who can say what they’re doing and back it up with evidence?
I’d like to think that my hypothesis is sound, but I’m employing a ton of motivated reasoning. This film could just as easily be rolling with all of those early concepts we saw just to make sure it hits the deadline. Rewrites take time, and bigger parts for veteran actors take a lot of negotiating. The simplest path for the studio to take would be to do just what the widespread percepction is – cut ties with the original and keep the original cast in the film as Stan Lee walk-ons.
We’ll see. 
