Ohhh! No, I wouldn't use -vaD there. First off, Gorkon doesn't say "to" in his toast, he just says, "I offer a toast: the undiscovered country." He wasn't offering a toast TO the undiscovered country; he was offering a toast to the people at the table regarding some vague wish about the undiscovered country. His vagueness is the whole source of the tension: in Hamlet, "undiscovered country" refers to death, not the future, and even when he clarifies that, he's not saying what he hopes for the future.
Undiscovered involves perfective (sorry). tu'lu'pu'be'bogh which one has not found. Undiscovered country, where country is understood to refer to a world or realm and not the countryside or a nation, would be best translated as qo' tu'lu'pu'be'bogh. You could use pagh as you did, with qo' tu'pu'bogh pagh.
I totally forgot we got tuch for future.
That -vaD would only make sense if you were saying something like qo'vaD tu'lu'pu'be'bogh SoQHomvam vIjatlh I say this saying to the undiscovered country, and then made some toast to it. That's not what's happening here.