Active ftp is dead. I wouldn't be surprised if browsers don't support it out at least don't default to it since as you said it would break things for 99% of users. Running a server that's not configured properly for passive transfers is effectively a server that's useless. So if it would make someone sleep better at night I'd be fine with removing active transfer support from browser clients. Switch to filezilla if you're a power user or want to do some 1337 FXP tricks.