In any case, the 17th Amendment did not accomplish for what it was sold to the people as a fix. It was, at best, useless, and at worst, subversive. After all, it is cheaper and easier to buy one man than it is to buy an entire state legislature, and if it can be done legally (with campaign donations or via indirect influence with issue ads), all the better. That is why direct elections did in fact lead, IMO, to an increase in the corruptive influence of money and special interests.
In general, governance works best when the power is pushed closer to home.
You are probably right that it never will happen. However, it could happen with the right efforts. State legislatures might be amendable to supporting it, since it would be a power grab for them. Using the campaign finance arguments honed by McCain, it could be possible to spin this move away from direct democracy in a populist manner. And since the progressives would fight this tooth and nail, an effort to do this would put them on the defensive for once, causing them to spend money to defeat something instead of them spending money to expand the socialist state.