Extremely confusingly the Ti stands/stood for titan as well, while at the same time Nvidia also released cards with the name "Titan", like the Titan X, Titan Xp, Titan V, Titan RTX etc. When people say "the titans" they may refer to either the "something Ti" cards or the "Titan something" cards.

The video[1] mentions that it (3090) was made for users in the Titan product segment, and it's introduced as a Titan replacement. The Ti models will probably come later as usual.

[1] https://www.youtube.com/watch?v=E98hC9e__Xs&t=34m14s