We have no way of knowing when they will release its shiny and there isn't much reason to expect it's coming any time soon. It's up to you whether you'll get more enjoyment playing in the now or if you think your patience for something we may not see for another year or longer will be more rewarded.
Latios Conundrum
I'm real tempted to dump all my rare candies into Latios (15/15/11) since it is such a beast in PvP. However, im worried its shiny form will come out soon and I'd of course rather power that up (if i manage to catch one).
What do you all think? Waste the resources now or play the waiting game?
Answers
The stardust count will also need to be considered. If you want to use it competitively in the Master league, it will need to be maxed and startdust is even more precious than ever. Even more resources required if you want to unlock its second charge move.
I wouldn't say the resources will necessarily be a waste though. Even if turns out to be underwhelming for you, or you find a slightly better IV replacement, it's still going to be useable in raids and as a gym sweeper.
Assuming it wasn't caught weather boosted, it'll have the right CP to be used in the Ultra League. Could be worth a relatively light investment for use there and see how you get on with it.
Latios is very good in PvP, most pokemon that have dragon claw are. I'd say theres not much of a risk for latios and latias getting their shinies for a long while, we only got the birds recently, the beasts arent out yet, we still have what could be a long time before niantic brings those legendaries back, the rest of the weather trio with their shinies likely will come first, you'll have plenty of time before they come back.
Hi! Logged in just to add my input-perhaps the OP is like me, where, I derive little joy from engaging in gym battles or raids, and although they provide tangible benefits, I have been playing since the launch solely to play against other in PvP (albeit has been a bit of a let down).
I do not have 'fun' playing in raids, I dislike engaging in conversation with a large portion of people I meet through this game, and I do not have fun in gym battles. For this reason, the OP, like me, may want to maximize the likelihood of winning, by using their hard-to-come-by resources, even though there is no in-game benefit.
But from a raid/gym perspective you are absolutely correct!