I knew a young couple who, about three to four years ago, were expecting a girl, and the husband wanted to name her
Isabella. The wife vetoed that because she knew how popular
Isabella is. What they named the baby instead was
Annabel. So I think you're right when you say "
Annabelle Grace is the new
Isabella Grace." Those who reject
Isabella due to popularity are likely to turn to
Annabelle or
Anabel because of the similarity in sound and style. You can already see that in Annabel/Annabelle's popularity statistics.