If Trump loses the election we'll have to discard him. The problem with you're train of thought is that you think the alt right finds trump to be ideal. That simply is not the case. What he does have is name recognition, money, and the right attitude, personality wise when it comes to saying what most Americans have been saying for years. He doesn't bother with PC garbage.
He's already performed a valuable service, regardless of how the election turns out. The Republican party has been put on notice. They now see the cost of disobeying the will of their own constituency. Republicans will have to change the way they run for office from here on out. Not to mention the way they vote once in office. Trump also has paved the way for future republicans with the same ideas, but in a more polished , and refined form. These next candidates will seem like a breath of fresh air compared to Trump, and possess the political acumen to garner the support of the newly molded Republican party.
It would be naive to believe that the rise of Trump was a flash in the pan occurence. It took at least 6 years to push Americans to the point, where they would tolerate Trumps antics. For the most part this behavior has been tolerated because a significant portion of the American public demands change. Trump, unlike any other candidate most of us can remember is truly symbolic.
The system/establishment despises Trump. A huge portion of the American public despises, and does not trust the establishment. Trumps popularity is merely the symptom of the disease that is our failing trust between the citizenry and government. And one thing is for sure. A Hillary win is about the worst possible prospect for curing that ailment. More likely it will fuel the fire.
Trump just happened to fit the bill at the time; but there are many additional options who are more politically capable. And now they have a voice, and what's more; now they will be heard.