I mean IP fatigue, stagnant formula and few signs of notable improvements from the team in terms of ideas and ambition. They are like GG before Horizon's announcement, they need fresh air.
To keep working on inFAMOUS can only lead to yet another more-of-the.same title. On the other hand, if they tried something new, who knows what a new inFAMOUS could become eventually? Easy example: the Uncharted franchise, that really took advantage of the dev. experience on The Last of Us.