There's the official poster of Kamen Rider Saber. Aside from Saber and Blaze, there are additional Kamen Riders who have joins the fray. Also, it's already identified who will become the Kamen Riders, though one of them hasn't identified yet.

　・Touma Kamiyama (神山飛 羽真 Kamiyama Tōma) = Kamen Rider Saber (仮面ライダーエスパダ Kamen Raidā Seibā)/Fire － In the middle.
　・Kamen Rider Blaze (仮面ライダーブレイズ Kamen Raidā Bureizu)/Water － In the left.
　・Kento Fukamiya (富加宮 賢人 Fukamiya Kento) = Kamen Rider Espada/Lightning (仮面ライダーエスパダ Kamen Raidā Esupada) － In the right.
　・Currently unnamed Kamen Rider/Ground － In the upper left.
　・Ren Akamichi (緋道 蓮 Akamichi Ren) = Kamen Rider Kenzan/Wind (仮面ライダー剣斬 Kamen Raidā Kenzan) － In the upper right.
　・Kamen Rider Calibur/Darkness (仮面ライダーカリバー Kamen Raidā Karibā) － In the upper middle.

https://youtu.be/o1EGkIX6GeY

There is also a special trailer of Kamen Rider Saber about its synopsis and the transformation.

Kamen Rider Espada (Lightning)

Kamen Rider Kenzan (Wind)

Currently unnamed Kamen Rider (Ground)