With Bigelow and Sierra Nevada both with inflatables (one in a proven state the other in mock-up) I think the station building might be contracted out. as will the launch services for construction and probably crew rotation.
I'd like to see it fly too, but lets be serious and honest. At only two flights per year (and that's a big stretch to think they could meet that) the SLS is too expensive to maintain.
As great a work platform as Shuttle was; if thought of in a critical manner, it really set us back. Down-mass capability was interesting, but how many times what it truely utilized? The crossrange was another plus, but man-rated capsules are eventually going to be reusable, and they are far cheaper to maintaing the TPS, as the tiles/ablative shielding is more easily replaced.
The SLS, eggs in one basket, really comes down to being a government work project. There was a tremendous brain-drain from NASA (and partners) as the Shuttle wound down. Constellation/SLS managed to keep some, but the planning was terrible. Side note -I need to dust off my 'Direct' projects for Orbiter and see if they would have been feasible as a supplement to Shuttle...
That all said, I don't think NASA is coming to an end. It's a smart organization when utilized. The problem solving skills of that bunch is first rate. And I think they will continue to work on the science involved with human/robotinc spaceflight, and exploration of the solar system.
A private corporation does not have the same motivations, meaning, they're in it for the money. Elon does have a philanthropic mission, but he needs money to get there. SNC, and Bigelow won't do it for free, and ULA builds rockets, they aren't interested in a floating hotel or a Mars (or Moon) colony, Bezo's is still kind of a wild card (to me). But NASA can work with them in partnership to accomplish the science, study, and expertise need as they have a government that provides the bucks.
It doesn't matter how much money and individual can front. Pooled together they all pale in comparison to what NASA can bring if they are properly funded.
This is all just my two cents though. I figure on the government to do the stupidest thing possible.