Update — August 16
All the information in this article is to be taken with a grain of salt, nothing has yet been confirmed by Riot Games regarding the 146th champion to join League of Legends. Nevertheless, if all these rumors are proved to be true, the small world of ADCs could be turned upside down.
By searching through Reddit and by cross-checking all the information, we start to see what the next champion could be. Riot Games had promised us "a new shooter who will break all conventions". This new ADC would be called Aphelios and would be a shooter... with magical damage. A first glimpse of the champion (the champion?) has apparently leaked on the PBE:
On a Voyboy video, we can see an empty box entitled "Aphelios" within its Champion Select.
Plus, a Youtuber — Majner — seems to have unveiled a big part of Aphelios' gameplay and history:
The following GIF illustrates the tweet of Riot Games when they announced their new Champion. A beam of light piercing through shadows does not really fit the gameplay we were described. Remains to be seen if all of this is true: your move, Riot.
While Ahri, Nocturne, Veigar, Galio, Varus, and Shen received new skins, some players discovered something quite mysterious within Elderwood Nocturne file. According to Surrender at 20, rather than discovering a new splash art of Nocturne, they spotted a mysterious young woman who doesn't look like any existing champion in League of Legends.
However, this young woman displays all the features that Riot unveiled within their Champion Roadmap in April 2019.
Riot have previously mentioned that they would rework Mordekaiser — as well as Pantheon — but they also spoke about a new ADC... The coincidence might be just a bit too much.
That's not Riot's first leak, especially regarding new champions: Neeko was also unveiled in December 2018 because one of her skins had leaked.