Since we know that the next two champions (Jungler and the Masked) are coming together during the summer event. According to this source, the OP found some files about the upcoming champions.
First one: “They took your home LILIA, do not forget this loss, let it course through you’
The Jungler will be released earlier is Lilia, and the voice in the first audio will probably the masked champion interacting with her.
Second line: “Oh lost spirits beckoning to bloom, I’ve been waiting for you”. Either way, this line also mentions the spirit blossom festival that is coming, where the spirits wait to bloom and talk to their old relatives.
However, someone has found that, these voices sound a lot like the one from Ruined King game teaser. Many people think that this new Masked champion may come from the Shadow Isles, or not. But if the new champion turns out to be the Ruined King (just a hypothesis), that would be awesome!
In the coming 10.15 patch we will expect the new Jungler to be released along with the beginning of the event and the next patch should be the masked champion.