Potassium channels help to repolarize the cell after depolarization. But if the potassium channels are blocked, potassium ions cannot flow out of the cell to increase the membrane potential. Thus, one would expect that, at least for some period of time, the cell would be "stuck" in a depolarized state.
How long can this state last? Can a neuron go on indefinitely in a depolarized state if potassium ion channels are blocked? Will it find some other way to depolarize the cell? Will the cell die?