I think that not very many existing customers of Oracle migrate off, but I have to think that they are no longer the default for new and growing businesses to move into. AWS seems to have become that, with Oracle not even the second-most likely option (that would probably be Google or Microsoft).

Having said that, Oracle is probably the COBOL of databases, in that it will still be around (collecting good $$) from its existing customers for a long, long time.