I realize statistically most teams don't make it out of division four but the in the US that division is full of bot teams and casual players. Any hardcore player like myself really shouldn't worry about the competition there. I may be stuck there a season or two while training my players but I will be back to division three should I relegate.
A D.IV league of bots and incompetent players is probably the exception rather than the rule now, and you really only need a few decent managers to make the league tough anyways, because only one team can promote each season. In addition the baseline level of competition is probably going up each season as good young managers move up from D.V and replace less active/talented D.IV managers, so there's less gimmies on the schedule. It's not on the level of what D.IV has become in Spain or anything, but that's probably the direction things are heading.
I agree you might have a decent chance of making it back up, just saying that the level of competition could be tougher than the last time you were in D.IV, and if you end up getting stuck down there for more than a season or two, you probably start to lose any advantage you had as a recent D.III team, and then you're just another D.IV manager trying to climb the ladder.
For what it's worth, by the end of the season when people have their training, GS, and enthusiasm in line for the playoffs, there's probably 6-7 teams in my league that will be able to put up similar team ratings to what you won your finals with last season. Not saying you won't have an even stronger team then you did last season if you get relegated, just that what got out of D.IV last year might not get you out in season 14, especially depending on the league.
I think if you're already up there, you gotta find a way to stay.