I don't think G5 is coming anytime soon, considering I feel like G4 is going to end up being the Persona 4 of the MLP franchise.
But, yeah, I hope it's great, and Hasbro actually tries making it so. Though for the artstyle and toys, I think they would try to replicate FIM's artstyle, with a few differences. Maybe like having a bigger variety of body sizes and stuff.
I also wouldn't mind if the toys had much more dynamic poses like G1-G3. Actually made the toys feel much more varied, imo.