What season she would have succeeded Celestia would be pure speculation. I got the impression Lauren would have made the show more adventurous. Like her husband, Craig, she would use characters already created to expand on them and not keep pumping out new ones.
Season 3 was planned as the last season from the very beginning, but Hasbro saw great success in it, so they pushed Mccarthy and the others. Larson said many times, that he had to change the script for Magical Mystery cure, so it feel like an actual ending.
I'm not saying action for 26 episodes all the time... Just a balance because for slice of life, you have the flaw of "topic scrapping" You have this vast and imaginative world and I would like to see more.. And thankfully season 5 and 6 did that.