It's not over until it's over!! I'm in the same boat as you with waiting, but since we don't know the official last date of interviews we don't know if they've stopped sending out invitations! It's tough to keep positive about this of course, but we've done all we can and now we just wait
I also don't know if Penn has something like an "internal interview waitlist" where they don't tell applicants they're waitlisted for interviews, and just offer interviews to them if another candidate declines. So who knows!