The news has been coming fast and hot for Supergirl in the last day. First, we have an official synopsis for the first episode of next season:
SEASON PREMIERE – Kara (Melissa Benoist) is surprised to find that CatCo has a new owner who has brought in a star reporter. New couples emerge and explore their budding relationships while J’onn J’onzz (David Harewood) receives an unexpected visitor. Jesse Warn directed the episode written by Derek Simon & Nicki Holcomb. Original airdate 10/6/2019.
Next, we have word that a certain Smallville alum, in addition to the just-announced Tom Welling, will be returning, but not in the way you might think:

TVLine confirms that along with Tom Welling’s Clark Kent (Superman is unconfirmed of yet), Erica Durance will return not to portray the character she’s portrayed on Supergirl before, Alura, but rather Lois Lane, of the Smallville universe.
Thirdly, and last but not least, Deadline reports that Cara Buono, of Stranger Things, and Mitch Pileggi, of The X-Files, will be joining Supergirl, playing Gamemnae (Buono) and Rama Khan (Pileggi), two ancient aliens with agendas counter to Supergirl’s.
Awesome news! Now we just need the Baum to complete the trinity for the Smallville Universe…