The FAQ on hyatt.com used to say that HGP members would get an email in August to opt in for an Mlife tier. I don't see that wording anymore...it looks like you have to do it in person at an Mlife desk in Vegas, right?

My Hyatt Diamond expires this month (Diamond challenge), but I'm going to Vegas next month...

At least I have the Hyatt credit card = Mlife Gold.