I'm going to make a wild prediction and say that Galio will soon see greater play.
I think the meta is shifting enough where he can fill a specific niche, and it's just a matter of time for somebody to showcase that niche.
His laning against Veigar is particularly good, and he has solid lategame scaling with an impactful ultimate and a sufficient amount of aoe and decently low cd. He actually fares pretty well against most of the juggernauts (he struggles against skarner and fiora (but then again, there are very few who don't))
So I think he could become a counterpick or a flex pick for top and mid. I wouldn't anticipate support play, but that's also a possibility.
And thus concludes my prediction, not taking any bets that it will come true.
To be fair, actually playing on LAN + getting to high diamond made me a much better player. I wonder when I'll finally start going even on NA. 63% winrate over ~62 games so far. Not exactly fakeresque, but assuming my performance in mid plat elo so far is anything to go by, i can probably finish this season diamond.
Galio is himself a pseudo-control mage. So long as his ult is up, he has the threat of basically winning the fight in a single button. Combined with some good poke that sets up the possibility of initiation, he functions as a middle ground between control and all-in. He's risky because missing the ult is pretty much a death sentence, but this is similar to the risk of running Orianna.
Like I said though, I feel like he'd be a counterpick more than a staple pick, but a counterpick is infinitely more use than he currently sees. Particularly against Veigar and Azir, I feel like seeing either of those blind picked can result in the Galio counterpick.