I prayyy that Twilight Sparkle won't be in G5. I'd be fine if they went back to other Twilights, but Ms. Sparkle was the center point of 9 seasons, we can all use a break from her.
And Tara Strong's voice in general. She is so many shows' protagonist, it doesn't hurt her to lose MLP.
I'd celebrate if the new show's ponies looked like that boxart and all had brand new voice actresses. I am really fond of Tabitha St. Germain but at the same time I wouldn't cry if all voices got replaced together with the characters.