I understand The grandchildren in question, who work as models, have been trading off their prince titles, which is something that royals should not do. This was first proposed by the Queen of Margrethe of Denmark, in May, but obviously the family had resisted, so she made the announcement now.
Denmark is a much smaller country than the UK. Also the monarch of the UK, is also the Monarch of some commonwealth countries, so I am sure when P. Charles stated many years ago, that he wanted to slim down the monarchy, he did not (at that time) include P. Harry, ie; he fully expected P. Harry and any future spouse continue to be working Royals. (It is H&M who have decided to step back).
However, there could be many changes going forward;
Maybe the entitlement to the title of Prince/ess should be only for the children (not grandchildren) of the reigning monarch.
Maybe it could be restricted to those who live in the country, or an option when they are 18.
At some point those descendents, not ending up the Monarch, have to start leading normal lives.