It looks like Ray Ozzie is planning to leave Microsoft the same way he came in – with a long, visionary message that outlines how the software company must evolve in the face of a changing market reality.

Shortly after Ozzie joined the software titan as its Chief Software Architect in 2005, he issued a memo to the company on “The Internet Services Disruption,” outlining the steps he saw the company had to take to face up to a change in the market towards a services-led model and what he described as seamless communications.

Now, just a week after the company announced he would be leaving the company, Ozzie’s back with a stern warning to his soon-to-be-former employer that Microsoft needs to ready itself for the world after the PC as users continue to think less about computers and more about applications.

For the most part, we’ve grown to perceive of ‘computing’ as being equated with specific familiar ‘artifacts’ such as the ‘computer’, the ‘program’ that’s installed on a computer, and the ‘files’ that are stored on that computer’s ‘desktop’,” Ozzie wrote. “For the majority of users, the PC is largely indistinguishable even from the ‘browser’ or ‘internet’.”

Ozzie warns that although Microsoft has made progress in many areas, he believes that competitors are executing better in a number of key fields, including mobile experiences, the “seamless fusion of hardware & software & services” as well as social networking.

“[I]t’s important that all of us do precisely what our competitors and customers will ultimately do: close our eyes and form a realistic picture of what a post-PC world might actually look like, if it were to ever truly occur,” he argues. “How would customers accomplish the kinds of things they do today? In what ways would it be better? In what ways would it be worse, or just different?”

Like his previous missive to Microsoft staff, Ozzie tempers the gloom and doom of his “evolve or die” message by noting that Microsoft has been through these shifts before, and outlining his vision of the path to the “new day” for which he titled the memo – the day of “continuous services and connected devices.”

“And so, as Microsoft has done so successfully over the course of the company’s history, let’s mark this five-year milestone by once again fearlessly embracing that which is technologically inevitable – clearing a path to the extraordinary opportunity that lies ahead for us, for the industry, and for our customers,” Ozzie concudes.

One last thought: How visionary is Ozzie? So visionary that his memo, which he posted to the Internet on October 25, 2010, is dated October 28, 2010. Sure, that was done entirely to be five years after Ozzie’s Internet Services Disruption memo. But it’s interesting to think that where Ray Ozzie is, it’s already Thursday.