The problem with this one, and may voter referendums that want to change existing law, is when the vote it set up and then results in a strict majority-rule result. We don't have strict democracy majority rule in this country, never have. If we did, we could have the majority (whites) voting to have <insert your favorite race ju jour) packed up and shipped out forthwith. Literally, that could happen.
As for the 17th Amendment, it probably sounded like a good idea at the time, and I guess it sounded good for the nearly 100 that people campaigned to get the amendment inserted into the Constitution. It was created to correct some nagging procedural problems with the election of Senators, but all it's really done is change the balance of power from that of the States and the Federal Government being partners to what we have now - a fundamental structural problem which, irrespective of the political party in office, or the laws in effect at any one time, has resulted over time in expanding federal control in every area.
From the time the notion of direct election of Senators was first proposed to the Amendment itself, it was like 80 or 90 years. The idea of repealing it began in earnest less than 10 years ago, and it'll probably take at least another 80 or 90 years for that to happen if ever. It's unlikely that directly elected Senators would back any other method, especially since the reasons stated for repealing it (Senators of being hostage to special interests) are largely the same ones that were used to get rid of legislature-elected Senators in the first place. I wouldn't hold my breath, that's for sure.