Please let him be doing the accent, please let him be doing the accent.
Speaking to The Hollywood Reporter for a series called "Creative Until You Die" -- about people still working in creative fields even though they're over 90 -- Van Dyke said, "This one supposedly takes place 20 years later and the kids are all grown up. It's a great cast -- Meryl Streep, Angela Lansbury and that guy [Lin-Manuel Miranda] from Hamilton."
I'm assuming he's not going to be playing the elderly version of Bert, his character from the original movie, only because having Mary Poppins return as a young woman and Bert have aged that much is legitimately very sad and, again, it's only supposed to take place 20 years later, when more than 50 years have passed in real life. That said, I'm still hoping that he does the accent. Not "even though" it was awful but because it was awful. It's famous now.