There is a big difference between operating more passenger trains and running them at higher speeds, and running true high speed train service. The following article does a fairly good job of explaining this:
http://www.progressiverailroading.com/norfolk_southern/article/States-are-delving-deeper-into-highspeed-rail-planning-but-are-the-host-railroads-onboard--23532
You mentioned Richmond to Raleigh. This is a fundamentally different situation from what exists from Alexandria to Richmond. For years there were two separate rail lines heading south from Richmond to Florida. One owned by the Atlantic Coast Line that ran through Rocky Mount NC and one owned by the Seaboard Air Line that ran through Raleigh. When the railroads merged they decided only one line was needed. Ultimately CSX railbanked the former SAL line running from Richmond to Raleigh. I believe it is this railbanked right of way that is being discussed as a candidate for future passenger service.
While it may be possible to construct the former SAL line for true high speed service, it is my understanding they are currently talking about 100 mph trains. This is well below the true high speed trains the Japanese and French have. This makes sense given that beyond Raleigh and above Richmond Virginia there is little possibility of true high speed rail operations. And remember that 100 mph is the normal top operating speed. Allowing for stops and speed limitations the average terminal to terminal speed might be 80.
Now the question is whether it makes sense to spend huge piles of money to construct a rail line from Richmond to Raleigh which in turn will require more piles of money to subsidize operations. Is there really enough potential passenger traffic to justify that? Also are you going to spend even more money to upgrade CSX and Norfolk Southern's existing lines to achieve slightly better passenger speeds in order to take advantage of that Richmond to Raleigh line? Would it be better to spend smaller sums to add trains on existing rails, including some that do not currently have passenger service? Or would it be better to devote that money to other uses.
High speed rail in much of the U.S. is a great idea...FOR THE EARLY 1960s. At that time there was extensive excess rail capacity which could have been tapped for potential dedicated passenger rail lines. Urban sprawl hadn't gotten out of hand. It was still possible to acquire new rail corridors relatively cheaply and to shape land use decisions to take better advantage of rail service. The replacement of propeller passenger planes with jets was starting to make regional air service less attractive. The interstate highway system wasn't fully developed and part of our psyche. Even in the 1930s we had the technology to operate passenger trains in excess of 100 mph, PROVIDED the roadbed was up to it. Once dedicated to passenger service, rail lines could have been updated to meet the requirements of much faster trains.
Now high speed operations are still a reasonable option in certain areas where there is both enough traffic to justify it and corridors that could be used to build the lines. Virginia may have the traffic north of Richmond, but we no longer have the corridors.