That's the week I'm there. It's spring break week (for locals, several states, and in Canada). My prediction is that whole week is gonna be booked up pretty quickly. Single ticket reservations at DCA have been unavailable that week for awhile - only a matter of time for the hoppers, too.
My understanding is the reservations don't impact park hopping. It's CAPACITY that will affect hopping.
Since they sell the same number of tickets every day, and seem to be selling out most days, the only thing I could see happening is the right set of circumstances that cause DL to reach capacity on any given day, and prevent hopping over from DCA.
For example, if everyone with a hopper that reserved DCA for the morning, decides to move over to DL after 1pm, and everyone with a hopper that reserved DL decides to stay put.
Anyone know if either park has hit capacity since they implemented the reservation system?