If you consider yourself one of the lucky people who haven't been forced to switch to Timeline yet, know that your luck may soon run out. According to Techcrunch, Facebook will force all of its 955 million accounts to use the new, more visual profile layout this fall in order to give everyone a consistent experience throughout the site.
Timeline was introduced in January of this year, catching some people by surprise. Facebook has been periodically forcing more and more users to make the switch since then; the rollout will merely be accelerated so that the transition will be complete in the next few months. Its recently announced revamped Photos interface is also part of the site-wide change, so expect to get the feature soon.
You'll know you're getting Timeline once Facebook shows you a prompt upon login, telling you when your new profile is going live. Make sure you edit your profile first before it goes public if you don't want friends and co-workers coming across old party pictures you forgot you had on your account.