You don't have to "change over". HTML5 is not replacing HTML4/XHTML1, it's extending it in several ways.
Go ahead and learn about it, because eventually you may want to build something that takes advantage of some of the new stuff.
html5doctor.com/ is a good site to read through.
diveintohtml5.org is a good walk-through, from history to now.
See the huge ginormous red warning at the bottom of this page: HTML5