If there's no such contract or nothing in it that forbids you, we insist that you reveal more future lore details. Otherwise, show us the section that says "talk about future lore, you're fired".
I assume they want to keep a element of surprise.I mean why watch a tv show if you know everything that's gonna happen?For a tv show,you just wait a week to see what happens next.
Thing is:For old champ & plotlines,people are more worried about surprised changes rather than updates. Let's say there is a champ name Bob.Before,Bob was an investigative report who wanted to provide the latest scoop on the happenings of Runeterra.With his trusty magic camera,he traveled all over,from the vast desert of Shurima to the icy peaks of Freljord,from the cruel streets of Noxus to the glorious towers of Demacia,& so on.The last "episode" had Bob on a boat from Bilgewater to the Shadow Isles. After months of silence,the lore team announced they changed bob into some pervert who like taking a picture of girls.
For old thing people had grown attached to,surprise reveals are more scary than exciting.I mean forget Bob,this happened to an actually champ 
Also,I see a common theme throughout Riot:Don't reveal or talk about things too early because people maybe disappointed or upset when shit happens that postpones it.I think Ao Shin is an example of this.They don't want to build up hype then fail to deliver because Steve forgot to save the data. So,we either get silence or disappointment.Pick your poison.
So,Surprise reveals & they don't want to disappoint people,that's all I got so far.Oh,plus they're going through some structural change of their team right now,I think.Now this should be the case if the lore team isn't full of dickheads who say,"Fuck the fans.They don't need lore." or anything like that.Hopefully,the lore team is full of passionate creators who wants to create good stories for our LOL characters & world;who care about the fans & their opinions/input.
EDIT:While it understandable that there are somethings that should be hush hush.I don't think It's acceptable for the lore team not to talk to players at all.Isn't Riot a company that promotes communications between Rioters & players?The lore members shouldn't quiet for months,regardless of the amount of content released.
we insist
Brah speak for yourself. I like surprises.
...we insist that you reveal more future lore details.
That's funny. Unless you're suffering from multiple personality disorder or schizophrenia, you must be trying to incorporate every critic of Narrative into this little "I want spoilers" tantrum. Really funny.
It would be one thing if there was some kind of established canon or working universe at hand. If that was the case, then I wouldn't expect any kind of spoilers or pre-release discussion or anything like that.
But in terms of lore League of Legends is a vacuum right now. We have a bunch of disparate pieces like the city-states and character backgrounds, but there's absolutely nothing tying them together or (perhaps more importantly) tying them to the game itself. It's been this way for months. Because of this I would expect some kind of public discussion (and yes, even spoilers) from rito.... or at least, I would, had my faith in the Narrative team not been eroded to nothing.
However, to take the question seriously (as it were).
There are clauses in most entertainment employee contracts called "Non-Disclosure Agreements," or "NDAs." Basically, you agree to not leak information that may be important to a company or you will be terminated from your employment.
It's burned Rioters in the past (Riot Nasus got burned for leaking some internal playtesting changes to a "friend" over Skype).
It's writing 101 to not reveal everything you want to do. Riot could be an exception, but I don't think they're going to send out rough drafts to players.
I don't want future lore details, to be honest. I want a discussion with the Narrative team on how things are going forward. Some basic stuff: Will the retcon actually tie things back to the game? Will existing champions have further character development instead of simplified stories? I don't need spoilers on the lore, but I do want them to be more able to communicate with the community here. A cool animation here and there is nice, but a strong discussion between developers and fanbase would be better.
Overall they can't simply spoil certain plot lines. It is appearant that they do have further plans for certain plot points(for example they teased us about braum appearantly never aging and only throw slight hints at kalistas backstory),but if they spoil them now,then there is no point in releasing them later.
Retcons are a different problem,however I'd say that most retcons are kinda forseeable. For example it was clear that nasus&Renektons backstory would be changed,due to the "other-world-stuff". The same goes for all the other "other-world"-champs(except for the void-champs as the void is an established place),they will all receive retcons,so be prepared for that.
Then there are the champs tied directly to the league,they too will receive retcons,so again its no surprise if they come.
And lastly there are champs who are too distanced from anything and while they are not necessarily going to get a retcon,they are more likely to get one.
