Obviously there will be two different games, the main one will be Sonic the Hedgehog (original) remade in 3D Adventure-like setting with Modern Sonic with a new story to reboot the series. The second game will be smaller 2D game, Sonic Adventure remade in 2D pixels without hub worlds and the playable character being classic Sonic or Boom Sonic. Because iizuka said so.
/totally a real prediction
no, but really, it's just marketing material. it doesn't say anything about the upcoming game(s). The reason Boom Sonic is on the promotional material is because of Fire & Ice and the TV show. They got classic Sonic cause he is iconic and captures people's attention who lost interest in Sonic after Sonic Generations.
but really... the game is so obviously Sonic Adventure 3 ;p
j/k
but i do think it's going to be a game that feels like an Adventure game, even if it's not SA3 by name. Just a gut feeling i have. it could be anything though, it's hard to predict Sonic Team.