May I resurrect this question since more and more (if now possibly most) of the Ancestry.com database record native URLs are being converted to the new "discoveryui-content" type structure?
From what I can tell, the database ID seems to remain consistent but the record identifier has changed for the new URL structure. For example, this template was entered last year into a WikiTree profile: {{Ancestry Record|6742|6780009}}.
That active link still works, at least for now, and lands you at https://www.ancestry.com/discoveryui-content/view/6780009:6742.
The previous URL structure native at Ancestry was "search.ancestry.com/cgi-bin/sse.dll?indiv=1&dbid=6742&h=6780009..." The new format for the same record is "www.ancestry.com/discoveryui-content/view/10766243:6742..."
I have no clue whether or not things are stable at Ancestry, but experimentation using the existing template with what looks to be the new record ID seems to work. In other words, {{Ancestry Record|6742|10766243}} takes me to the same Ancestry record as did {{Ancestry Record|6742|6780009}}.
If that's the case, life is actually simplified somewhat...so long as Ancestry doesn't retire that old record identifier since it appears nowhere in the new native URL. However, the template information page at https://www.wikitree.com/wiki/Template:Ancestry_Record still shows only instructions on using the old &dbid= &h= URL structure. Should that page be updated so that folks can understand how to use the new Ancestry URL structure...assuming we think the template will continue to function with just that one change to the record identifier?