Champions who definetly will receive a voiceline update
Considering that the Summoners and Institute of war are no longer canon, Riot has made big effort to remove any leftover traces of it, involving champions talking to the summoner.
The most recent update of such was Lee Sin who got lore and voicelines updated to remove his part in that old lore.
However, some champions are still in possession of dialogues or lore parts connecting them to the old lore, being:
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Cho'gath
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Miss Fortune
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Ahri
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LeBlanc
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Nidalee
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Brand
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Fiddlesticks
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Edit: Sona as well.
Knowing that, it is downright guaranteed that they will get a voice over at the very least, with Fiddlesticks getting a full VGU sometimes soon.
???

Poor poor Alister.
? I'm not saying his voice is bad, but he could use interactive dialog like for example to have one between him and his adoptive sister maybe?
probably