The problem with this theory is as Konig states, Kormir had literal interactions with Lyssa before the gods left Tyria. That interaction recorded in her diary shows that Lyssa was present at the time of departure so it wouldn't fit any scenario where Lyssa would be consumed by the Elder Dragons.
At most, only Balthazar fits the scenario of being consumed by any Elder Dragon, and that's an aspect we had to fight _inside of a dragon_. If Lyssa, or any of the other Gods sans Balthazar, had any interaction with the Elder Dragons before their departure, more than likely they simply attempted to keep the dragons dormant for as long as possible. Past that, there's no real record of direct confrontation between the dragons and the Gods (one that would cause the twins, or any of the dragons, to consume Lyssa) until recently. Balthazar was adamant in taking on the Elder Dragons, making him the only real God that wanted to have any direct confrontation with them, and that didn't happen until after Lyssa, Kormir and the rest of the Gods imprisoned him in the Mists. The Gods always knew of the Elder Dragons as being part of the natural laws and balance within Tyria, which is more than likely why they never wanted to touch on the subject matter, or even interfere with it to begin with.
I doubt they would do that given they have free players. At best, they'd add the decors and have similar events between the two locations but I doubt they'd put that much effort into it.
