Quoting Wikipedia: (Emphasis mine)
Following its immediate predecessors HTML 4.01 and XHTML 1.1, HTML5 is
a response to the observation that the HTML and XHTML in common use on
the World Wide Web is a mixture of features introduced by various
specifications, along with those introduced by software products such
as web browsers, those established by common practice, and the many
syntax errors in existing web documents. It is also an attempt to
define a single markup language that can be written in either HTML or
XHTML syntax. It includes detailed processing models to encourage more
interoperable implementations; it extends, improves and rationalises
the markup available for documents, and introduces markup and
application programming interfaces (API)s for complex web
applications.2
The D in DHTML stands for "Dynamic" which means javascript, HTML5 is simply predecessor of HTML as described by above wiki article. This means DHTML isn't predecessor of HTML5.
Compare the definitions of the two:
DHTML:
Dynamic HTML, or DHTML, is an umbrella term for a collection of
technologies used together to create interactive and animated web
sites1 by using a combination of a static markup language (such as
HTML), a client-side scripting language (such as JavaScript), a
presentation definition language (such as CSS), and the Document
Object Model.2
HTML5:
HTML5 is a language for structuring and presenting content for the
World Wide Web, a core technology of the Internet. It is the fifth
revision of the HTML standard (created in 1990 and standardized as
HTML4 as of 19971) and as of September 2011 is still under
development. Its core aims have been to improve the language with
support for the latest multimedia while keeping it easily readable by
humans and consistently understood by computers and devices (web
browsers, parsers, etc.). HTML5 is intended to subsume not only HTML4,
but XHTML1 and DOM2HTML (particularly JavaScript) as well.1