I still believe Shiron will evolve. I'm convinced a Mohn rescue episode is happening, otherwise why show that Lillie is getting closer in the Alola episode instead of them just already being back with Mohn or just leave out Lillie at all and just say she's still looking instead of showing it so explicitly.
They could've just as easily NOT shown Lillie at all, or had her a few second still picture without her talking while another classmate narrated. Arcues know they didn't need to show Gladion at all, let alone give him dialogue.
Chances are they won't do anything with it, but that's a fair distance to go for an update that could've been handled a lot simpler or even not at all.