That image got confirmed recently to have been faked, though the Tweet by Jorge is real. El Tigre is making it regardless though I am sure.
My guess on new characters is:
Squidward
Jimmy Neutron
Raphael
Donatello
Vlad
El Tigre
Mr. Krabs or Plankton, preferably Plankton so we get another villain
Zuko for cool character
Otis for new series
I am guessing Invader Zim will get another rep, so Membrane for WTF and maybe Dib for unexpected
Mystery is either Fanboy & Chum Chum, Timmy Turner (They beat the legal battle), or potentially a wider Nick character like Tak or Rango.
Personally, I think Avatar, Zim, and Jimmy Neutron are probably the best IPs for more characters outside of SpongeBob and TMNT. As for new IPs, the biggest would be El Tigre, Barnyard and FOP. The things that I think could break my assumptions is them adding Arnold or another Danny rep like Sam. As for the rest of the series, they aren't really popular enough for another character or have other troubles such as Nick refusing to add the babies in the case of Rugrats.
Could they circumvent the concern of Rugrats being babies with their All Grown Up counterparts? Then again, that'd be awkward since AGU is practically a pre teen drama.
Damn, if only Randy Stair was still here to witness this marvel.
Looking at it, Ember's art seems kind of off. Also find it weird how Hey Arnold would get two new characters yet neither one is Arnold. That and Azula over Zuko?
If this is the final roster, it is pretty shit NGL. I like Plankton, but the rest feel like they are making the same mistakes of All-Stars 1 while also doubling down on the already over-bloated 90s picks.
I never considered the grandma from Hey Arnold being added to the roster, but after seeing that image and thinking about it, she could be a fun character.
My picks are gonna be:
-Denzel Crocker
-Kappa Mikey
-Otis or Pig
-Fanboy and Chum Chum
-Muddy Mudskipper
-Carl Wheezer
-The Catscratch trio
-Krang or Bebop and Rocksteady
-Bessie Hagglebottom
-Vendetta
-Mr. X
-Surfshack Tito
-Drake & Josh
-Carly
-Dan Schneider or the Nickelodeon foot
Nick games seem to completely neglect everything in between Avatar and The Loud House that isn't TMNT/Korra. I am shocked we are even getting El Tigre given this fact. I hope DLC pulls through as it seems like Nick wants to completely neglect the late 00s and early 2010s.
Would not hold out much hope for Tak, Tuff Puppy, Planet Sheen, Fanboy & Chum Chum, Back at The Barnyard, Making Fiends, Kappa Mickey, Mighty B, Breadwinners or Sanjay & Craig.