Considering we're in their turf, the borders are pourous, and their numbers as history has proven can be constantly replenished, I'd say the odds are in their favor.
I give Israel as the best example. They are not limited in tactics and methods like we are. They have gone to extreme measures and have had no qualms about taking out top leadership.
It is very difficult to fight an enemy that has engrained in their minds a centuries old mentality of warfare against infidels. Guerilla warfare is natural to them as well as actually throwing ones body to the battle.
Honestly I think the best hope is to take out the braintrusts of these groups. They will always try to hit us. But if we limit them to Molotov cocktail type attacks, we're better off than Khobar, WTC, Madrid, Bali, etc.