Very probably, no (not with the relatively simple development history you assume - reality is much more complicated). Dialects are really sticky and persistent - And also considered part of the local cultural heritage. They tend to assimilate and adapt, but also tend to stay. They influence pronounciation, grammar, and also choice of words to various extents. Even if dialects are superseded by hochdeutsch, the still tend to have influence to various degrees on some or all of the aspects. "Dialect" vs "Standard German" is not like "black and white" - There are various degrees of in-betweens (I would even consider the rolling "R" (The "Carolin Rrrreiber-R") used by some bavarian dialects even in Standard German as a remnant of dialect).
There are, however, regions within Germany where the local dialect is considered identical to hochdeutsch (for various historical reasons, mainly because the original niederdeutsch "dialect" spoken there would rather be considered a different language and is mainly extinct today - but this is highly disputable) - This area tends to get mainly located in the region around Hannover. Up until the 20th century, the German spoken in Prague was considered to be the "best" Hochdeutsch (but it obviously not superseded a local dialect there, as the local language has always been Czech).