I don't know if it will be Sanders specifically, but there is hope for third parties in the future if the last election is anything to go on. In the 2016 election, while still not coming close to winning any state except Utah (more on that later), third party candidates overall gained an increased percentage of the vote in every state. I think that shows the American people might be getting fed up with the two party system and want something different to vote for. If that is the case and the trend of third parties getting a larger percentage of the vote continues, they could become a viable political force in the near future. This is especially true with a number of states considering changes to their voting laws which would create a more favorable environment for third parties to compete in.
Now as for Utah: I think a third party presidential candidate could actually win Utah in 2020. Why? Consider this: In 2012 third party candidates in total only managed to garner 2.4% of the vote in Utah while Romney got 72.8% and Obama got 24.8%. In 2016, Hillary only got 27.5%, which is to be expected since Democrats aren't exactly popular in Utah. However, Trump only managed to get 45.5% of the vote to win the state. That means in the span of a single election cycle, support in Utah for third party candidates jumped from 2.4% to 27% which was the most dramatic gain third party candidates made in any state in the 2016 election. The reason? Mormons in Utah don't like Trump. And since Trump is likely to be the Republican candidate again in 2020, I doubt he's going to get much more support in Utah than he did in 2016. So if the right third party candidate comes along (perhaps Romney runs as an independent), that candidate might just be able to steal Utah.
That would be a significant political victory for third party candidates, even though it still wouldn't bring them anywhere close to the presidency. The last time a third party candidate won a state was 1968, so winning a state again in 2020, especially in light of the increasing support for third party candidates, could embolden more people to actually vote third party. Before you know it, they go from winning one state, to maybe winning two or three, so and and so forth until we finally get a president that doesn't have an R or D in front of their name.
Even if it doesn't lead to a third party victory, a third party candidate taking a state could serve as a wake-up call to both Democrats and Republicans that the American people are getting fed up with them and their increasing polarization. Increased support for third party candidates could force the Democrats and Republicans back towards the center in order to win back the increasing number of disillusioned voters.