We did Dresden, Weimar, and Leipzig as a trip a few years back. Weimar is every bit as fascinating as Dresden, albeit without the baroque architecture. This time, we'll combine Dresden and Prague. I was in Prague last in 1993 when under Soviet rule. I expect it will be a very different experience in 2016.

I wrote to the concierge at the Dresden Hilton who of course confirmed what stut said.

Unfortunately there are no regular ships running upstream from Dresden to Prague.
Some charter lines offer cruises with "hotel-ships" from Hamburg to Prague, but this is not what you want - and!
They often have to stop anywhere along the river due to low water and then bus-shuttle their guests.
This is something you won´t have either!
Maybe you do a daytrip by paddle steam boat from Dresden to Saxon Switzerland and back
and next day have a 2,5 hours train ride from Dresden to Prague?

Is anyone familiar with the day trip she recommends? Are there interesting sights in Saxon or is it move about the ride on the river?