DC-BAL-PHL-NYC-BOS is already a heavily trafficked rail and air route. If high speed rail showed up competitively priced with airfare and without the hassle of getting to/from the airport and going through security it would be used a lot.
Some plans have quoted a time from BAL-DC of about 15-20 minutes. That would make it an extremely popular commuting option for people working in DC, but wanting the cheap housing in Baltimore, which would also help Baltimore (although at the cost of probably making it not-so-cheap anymore).
Replacing short-hop flights would also be great for the environment, since most of the fuel is burned getting up to altitude and then back down again.
Some plans have quoted a time from BAL-DC of about 15-20 minutes. That would make it an extremely popular commuting option for people working in DC, but wanting the cheap housing in Baltimore, which would also help Baltimore (although at the cost of probably making it not-so-cheap anymore).
Replacing short-hop flights would also be great for the environment, since most of the fuel is burned getting up to altitude and then back down again.