Questions about current flow, power supplies, and floating/grounded loads
In this case, wouldn't there still be some current flowing to ground
  until the supply runs out of juice, being that there's no return path
  for the electrons?


No, because as you have noted, there is no return path.


  Second, knowing that there has to be a return path for the current
  back to the supply, how is the current returning for the floating
  load?


Because, as you note, there is a return path. A power supply will use a transformer for reasons of isolation and this, effectively, makes a floating voltage source.


  Wouldn't the current seek straight to ground now that the jumper wire
  is there


Ground is not a viable return path for current - current will want to return to the supply source negative terminal.

Imagine that instead of planetary ground or earth, these circuits were on a space craft and the ground connection was just the space craft chassis - would you see things differently?