Great question! We are actively working on a blog that will compare flooding tools - to include the Flood Impact Analysis solution, the new Flood Simulation tools, and ArcHydro - and how they work together.
The short answer is that the Flood Impact Analysis solution will continue to be supported, and there will be options to use both Flood Simulation and the Flood Impact Analysis solution together.
We are planning on having the blog out in the near term. I'll share the link here once it is posted.
