So, agent 08 has been a mystery all game with new agents being added and being agent 14, 15, etc.

The Year 1 event announcement for the new agent has these names crossed out: Cypher, Brimstone, Omen, Sova, Jett, Sage, Viper, Phoenix

Notice anything familiar about these names? They were the first 8 agents that were released with the game in early press builds, as can be seen in this link: https://www.gameinformer.com/preview/2020/03/02/valorant-preview-a-deep-dive-on-the-new-hero-based-tactical-shooter-from-riot

So since there is nothing else in common with these names, it is probably a hint that the new agent is someone who has been part of the Valorant protocol since pretty early on, went missing for some reason, and is now back. This, along with the release of the cinematic as well as having the creative director publish an article on it, is probably a sign that Valorant is going to have a pretty big story push soon.

Note: the vowels missing from the names is probably for artistic choice to shorten all the names to fit on the banner. I don't think that's very relevant to being a clue.

It has also been reported that sometimes when you refresh the page, the "new agent' banner has a clean version where all the names are removed. The author of the announcement article responded with a cryptic "Batman thinking" gif when asked about it on Twitter. Proof: https://youtu.be/PINGV7-tr_0?t=169

TL;DR: Agent 08 is the new agent, as the names crossed out are from the first 8 agents released.