Gore's endorsement effectively sews things up for Dean. It is a very big slap in the face to Bill Clinton, and an attempt to take control of the Democrat Party away from the Clintons.
The only way the Clintons can now keep control of the party is for Hillary to enter the race. Otherwise, the party apparatus is handed over to the far leftists and Dean. I am certain Gore extracted some concession in this regard from Dean's camp in exchange for the endorsement.
Gore wants to run in '08. He has no chance if Hillary runs. So he is effectively defanging the Clintons now, trying to draw Hillary in early. The Clintons' lapdog Clark is going absolutely nowhere, so it's Hillary or nothing if they want to retain control over the party and its pursestrings.
The Clintons' response has been to withdraw and form shadow organizations for collecting soft money. I think you can take this as a sign that Hillary will not run, and that they will marshall the resources for their '08 campaign from outside the party establishment.
Still, the Dean nomination is a setback to the Toons' future ambitions.