What did the content of the email state exactly?
They are probably inviting you to upgrade to the outlook.com interface. (If you don't like the new look, you can always hit the "gear" and then "switch back to Hotmail") You can "upgrade your interface" at any time by just going to outlook.com and logging in with your Hotmail account.
I'm fairly confident that Microsoft is NOT sending out emails to ask people to change their email address, and it's not going to change by you clicking a link from an email (which is probably just to outlook.com). You CAN change your email to @outlook.com... but it would require a hard reset on your phone of course.
If this helps, right now Microsoft has REMOVED the functionality to rename your account since they had a few problems with it. So even if you wanted to you can't change/rename your email address at this time