Can I convert a US Topo from GeoPDF to GeoTIFF format?

Yes, it is possible to convert GeoPDF to GeoTIFF using both commercial and open source software. Two methods for separating US Topo layers and reformatting as GeoTIFF are documented in a paper. This paper is revised at irregular intervals; interested users are encouraged to check the link in this FAQ occasionally for updates.
 
Some additional information, mostly about reformating with commercial graphic art software, is in the US Topo and Historical Topographic Map Users Guide.
 
The paper referenced above also discusses GeoTIFF reformat of maps in the  Historical Topographic Map Collection (HTMC). However, as of April 2015, the National Geologic Map Database project's TopoView application serves GeoTIFF versions of HTMC maps. These will eventually be served through other interfaces as well.
 
USGS has no plans to create standard GeoTIFF versions of US Topo maps, as the multi-layer nature of US Topo does not lend itself to a single, simple TIFF product.