Not totally accurate, but close.
First, you are missing three FCPS teams that are now Class 5A North – TJ, Edison, and Stuart. Also moved to 5A North from the NR (but not FCPS) are Wakefield and Stone Bridge.
Second, there are still District Championships (at least for football) and they will be determined, as they are now – best record against district opponents.
Third the top 16 from class 6A North and South will play until there are two teams left – how they deal with the final 4 has not been approved yet – one option is to cross bracket so the best in 6A North plays the 2nd best in 6A South and vice versa – that would theoretically lead to the best two teams in the final – the other option is as you describe it – champion of North plays champion of South.
FYI the Non NR teams that are now in 6A North are: Battlefield, Stonewall Jackson, Osbourn, Osbourn Park and Patriot. Also there are significant changes to how power points are computed but the details are two complicated to go into here. If interested go to
http://www.vhsl.org/classification.alignment-2013-15.