I originally posted that answer backn in 2016, but l have to agree with The Reductions I don't think teams can relegate to D5 anymore unless all spots are taken in all the D4 leagues.
But if you have landed in the 8th you still get relegated in a way but to a different league if I'm correct.
So, if you want to get out of a league there are still two ways to get out.
I hope this answers your question, good luck and I hope you enjoy this game.