On Janine…
Actually on second thought..I bet you guys anything she'll look much like she did in GB2.
Oh, please God, no…
On Louis…
As Roshanger once put it himself, I believe:
“Rick Moranis=Good”
“Louis Tully=Bad”
He's a lousy Ghostbuster, for one thing–Winston, Venkman, and even Dana and Janine (even the fake one from RGB Seasons 2-6) have him beat when it comes to the physical qualifications (being able to fight, aim, and lug a heavy unlicensed nuclear accellerator on his back; the physical stats in Ghostbusters International bear this out); Ray and Egon aren't exactly the pictures of physical perfection either, but they are absolutely unbeatable when it comes to knowledge of the paranormal and science.
And what is Louis's role in the company? Accountant and lawyer. And they had to actually make up and graft the latter persona onto him to put him in GB2 at all. Not much opportunity for action and comedy there (as they put it in Ghostbusters International: “Don't overuse lawyers–there's nothing funny about them”).
So what's left? His “relationship” with Janine? Janine already has a well-established love interest, and his name is Egon.