I think the only thing that will get Riot to look at supports again is if it again becomes a huge problem in champ select where its causes lots of negative drama because no one is wiling to support. Sure that still happens but much less than it use to and I think from Riots perspective thats good enough.
Riot has shown through their actions of nerfing any support champ or items that dares disrupt the health of some other lane that they consider support a second class lol citizen whos needs always take a backseat to the needs of the other more important roles.
Maybe if teambuilder que times get super long primarily because no one will que as support that could prompt Riot too.
Basically just look for when the lack of interest in playing support impacts peoples abilities to play the other roles Riot finds more important and then you will probably see more positive attention given to supports. Until that happens though, Riot wont do shit. They will just say they are happy enough with how things are and would rather put their attention to areas that need more help (translation: to roles that they consider more important).