You will be waiting more than a few months if you want to wait for Windows XP (and Server 2002, as they plan to call the server-side products). Because XP Professional will not ship until 10/25/2001, the first exam (the equivalent of 70-215 for Windows XP) will not be ready until March or April of 2002.Likewise, the other exams will not be ready until later in 2002.
Thus, you are talking about waiting a year for the new versions or getting started right away. If you want to get moving sooner rather than later, and maintain the currency of your MCSE into 2002, go for the Windows 2000 stuff.
This was first published in May 2001