Yes, the Azir one did feature Sivir and a few others (though said others were not made in CGI), but I doubt Riot will settle for just making videos for new Champions or for remaking old ones. A New Dawn was awesomesauce, and I look forward to more.
But on that note, who do you want to see in those future cinematics?
My picks are 
, 
, 
, 
, and 
, at the very least.
Shyvana, I would love to see how the relevant cinimatic team interprets her transformation, her W, her.....you know what, let's just go with everything.
I would like to see a cinmetic with all the Battle-CAST 
fighting against the mechas 
with some epic background music, maybe for a promo for battlecast kogmaw or something like that xD.
I'd like to see more spooks and more flashy magic based champs. Like 
. Also crabgot.
Maybe just a cinematic of a day in the life of crabgot. Like he wakes up, alone, in his studio apartment in Noxus, shuffles over to the mirror, takes a deep breath and just sighs.
My picks are; 
(She became pretty popular :D)
And 
for the other team.
"banish the darkness"
vs
"surrender to darkness"
What I want to see would be a 
fight each other in a cinematic.
Though, they already did Rengar, I would just love to see the two duke it out. And 
being in there would be icing on the cake. as for anybody else.
I am thinking... 
I would love to see them do more bestial champions like Rengar. He's my favorite champ and it made me so happy to see him in a cinematic.
Renekton would be a wonderful choice, as would Hecarim. I'd also like to see Mordekaiser, and a yordle, maybe Kennen.
I'd like to see all of my favorite champions, of course.
The ones who haven't already been in cinematics, anyway. LeBlanc, Malzahar, Varus, Karma, Viktor to name a few.
But honestly, I'd just settle for Katarina not being in the next one. I know she's iconic, but I'd like to see more variety.
would be pretty awesome with all the special effects you can do with his abilities, would be amazing to see in fighting action but I understand that animating all his effects and motions would take forever and need to be done with painstaking precision so that he doesn't look crappy.
could have great fight scenes where he constantly is switching between sword and gunplay
due to how crazy he would be like in fight scenes
, , 
, 
and
