There was no EM elective available for my class (co 09 M3s) because the person who organized it left a year or two ago. There's a peds ER option during peds for a select few. It's always been an elective for M4s. Next year it'll be available as an elective for M3s.
I don't think I'd like for it to be a requirement. We have so many other required things 4th year, it's really annoying.