There was no chance whatsoever of the Shadows, or any other first ones, interacting with the aliens from Thirdspace. Ivanova found that gate on the way Home from saying "Goodbye and Good Riddance" to the First Ones.
You can be sure that, if there had been any Vorlons left when they found that gate, they'd have shown up. Judging from what they left in Lyta's mind, it scared them to death the first time around. They sure wouldn't have wanted anyone to open it again.
The Dialogue in the movie was pretty clear that the gate Had to be opened in Our universe. So, unless someone built (or builds) another, we've seen the last of them.
Since it took Vorlon tech to build the first, I'd say it'll be a long time before anyone is capable of building another.
Also, you can be sure that the Vorlons never built a second and that the other First Ones probably learned from the Vorlon's mistake. From what we know, it probably took More than just the Vorlons to beat back that first invasion. If they'd won on their own, I doubt they would have considered opening the gate such a big mistake.
------------------
Yes, I like cats too.
Shall we exchange Recipes?