I don't delete accounts. I tell them they can simple stop using the account and I will remove personal details if needed. But I like to have their IP on file for all my members as I've had trouble with trolling in the past related to this topic. I also have had many come back regretting they deleted it. So I just keep them all as is with personal information blacked out to the public view.
I wouldn't be surprised if they just port over the 3.X version of chat. Chat has always been severely neglected by IPS for some reason, so many areas they could improve or directions they could take it. I'm not holding my breath though.
I noticed others, like myself, were having some minor difficulties related to the email settings in IPS4.
1) Check what email your are using in the "From" field. Some hosts only allow that email to be one that is created in cPanel, as opposed to an outside service. 2) If you are having time out errors related to your SMTP settings, contact your host. My previous host never restricted certain ports, but the one I am currently using had the port Mandrill uses closed which was resulting in those errors.
Both of those fixed both the PHP and the SMTP email settings for me, hopefully it will help someone else too.