I think the way this plays out will entirely depend on the CM at the ticket booth. They are given a lot of discretion. But, if you are upgrading before your last day, I really think you will have to add MP to the 4th day (otherwise how would they know which days MP was valid?). Also, keep in mind that you can only upgrade to a ticket with equal or greater value. I haven't compared the price of 3day+MP old price to 4day+w/o MP new price, but the new ticket has to have greater value.
As far as MM goes, you are not suppose to get it at the ticket booth. But, last year when I upgraded from a 2day to a 3day, I made a comment to the CM about being disappointed that I wouldn't get MM. She just said, "Oh, I already added it to your tickets!" It was nice pixie to start our trip. It's difficult to plan when you don't know exactly how an upgrade will go, but as I mentioned above, so much depends on the CM.