I forget - have the Gerudo been portrayed as allies of the royal family/Hyrule before? I only remember them being in OOT, where Ganon was their king, but they seemed not to be allied with anyone. Maybe they'll again go the route of it being the guardian/whatever Gerudo woman in the trailer who allies with you and the others are more neutral or hostile. They do have a city in the trailer though, so they are presumably at least somewhat friendly.
In the Official Timeline there was a Civil War/Unification War before OoT that caused OoT Link's mom to die. The events in that war are super vague, but after the war the Gerudo "once again" swore allegiance to the King of Hyrule. This suggests that they were allies before that war. Ganondorf of course was insincere about his allegiance and ends up betraying Hyrule. This causes the events of Ocarina of Time.
It seems the Gerudo are okay allies but Twinrova and Ganondorf really seem to sour things consistently. At the end of OoT (Adult Timeline) the Gerudo are happily dancing and celebrating Ganondorf's defeat. There's a chance they were very oppressed by G-dorf as well. The carpenters mention mass brainwashing and the Iron Knuckles are clearly mind controlled Gerudos. They weren't evil just heavily manipulated. Quotes from the carpenters:
"The leader of the gang of thieves
is Nabooru. She is experimenting
in brainwashing many people at
the ruins in the desert.
Oh, it was Ganondorf the Evil
King who was behind the gang of
thieves...
When Nabooru was a lone wolf
thief, she never stole from
the weak, but...
Now, Nabooru's gang of thieves
stands for cruelty and brutality.
She claims to be a chivalrous
robber, but...no way!"
"Like I suspected, Nabooru was
brainwashed by Ganondorf's
followers..."
In Four Swords Adventures the Gerudo are considered noble and true and definitely trustworthy...which is different from OoT. The Red maiden says
"The Gerudo honor the desert.
They are trustworthy and
pure of heart.
I cannot imagine one of them
is the King of Darkness..."
This would suggest that when super evil Ganondorf isn't around the Gerudo aren't actually hostile. In FSA the Gerudo actually brand Ganondorf as a criminal before anyone else learns about him. It seems that late in the Child's Timeline Hyrule and the Gerudo are friends. Although early in the child's timeline a lot of fans theorize a war between the Gerudo and Hyrule before TP that led to the Gerudo being pushed out of Hyrule or even close to killed off altogether...
In the defeated timeline...I have no idea how they are. But overall I'd say they are isolationists and reluctant allies to Hyrule.
If I were to give a run-down of the Gerudo throughout the timeline it would go like this:
Between SS and Unification War: Allies/neutral
Unification War: Enemies
Ocarina of Time: Enemies (Under Twinrova's magic)
(AT) Before Wind Waker Flood: Allies
(AT) During Wind Waker: Gone?
(CT) Before Twilight Princess: Enemies (Under Twinrova's magic)
(CT) Twilight Princess: Gone/Chased out
(CT) Four Swords Adventures: Allies/neutral
(DT) Imprisoning War: This is anyones guess. They could've been turned into monsters, or they might've ran off/isolated themselves.
