Well, not just rumors now. More pics for
Goukaiger:
Spoiler for Mecha: GoukaiOh toy images:
Base mecha:
It's main ability is combining with mecha from previous sentai, some of the initial combos:
Magidragon (Magiranger)
Magi GoukaiOh
PatStriker (Dekaranger)
Deka GoukaiOh
Gaolion (Gaoranger)
And Gao GoukaiOh
Not sure what the black silhouette at the back is supposed to be