The video with them seeing each other again had definite tension between them, I'm sure we'll get more about their relationship once Riot decides to release something related to Mount Targon in the future. Problem with League lore is that since there's like 200 characters, you usually have to wait ages for the next bit of lore for a specific character
So far the only exception to that are all characters who appear in Arcane, which is progressing much faster for obvious reasons. Vi and Caitlyn are 100% going to be canon, otherwise that would be the bait of the century. And who knows, maybe there'll be a show about Leona and Diana in the future? One can only hope