When you just starting to feel comfortable with HTML4 with strict XHTML specifications, others are starting to make their websites HTML5 ready... like a never ending learning. Is this really a big deal?
No, don't worry... it won't be your problem. HTML5 or HTML4 or XHTML, your site will still be read by modern browsers. In other words, browsers are becoming more and more intelligent, and they do understand what you're doing with you're markups even if you don't post the W3 Doc specifications. As I see it, these W3 doc specifications are just for backward compatibility of browsers reading old codes. Well, why not just update those sites? It will save browsers, developers time and energy from maintaining these backward compatibility features.
We are in the age where dynamic content and markups are possible to live independently from each other (content is stored separately from markups). Millions of web pages are being published and updated daily using this method of separation. It's not anymore realistic and practical to maintain old standards for sites which have not been updated its system. We should not baby-sit these old sites, if they can't join us, let them die a natural death, otherwise these old standards will hold us back... it's like the IE6 curse.
HTML5 holds a promise of easier and user/developer friendly ways of dealing with media types such as audio, video, image, graphics, etc., which all have subtypes, and features that will simplify form creation, validation, and submission, and much more...
To know more about what you can actually do in using HTML5, visit this site: