Not happening. The Libertarian Party had their best chance ever in 2016 to make real gains, yet they again ran an absolute disaster of a candidate in Gary Johnson who was as likeable as a brick wall. I voted for the guy but he did absolutely nothing to seize upon the opening that Trump/HRC gave him.
Besides, the D's and R's basically have multiple parties within the party already. An R from New York is totally different from an R from Texas. Same with D's. Joe Manchin is nearly the antithesis of Pelosi yet they share a party.