10 Stargate Storylines That Were Never Resolved
4. Are All Of The Tollan Dead?
The Tollan were an extremely advanced race, one which Daniel Jackson speculated had descended from humans kidnapped by the Goa'uld thousands of years prior. They were extremely isolationist and it took time for them to come to trust humanity, though their isolationism also fed into their lack of understanding some of the threats that were out there.
When Anubis returned to the Milky Way galaxy, he sent his emissary Tanith to Tollana, shattering their deeply held belief that they were more advanced than everyone else - Anubis's ships manage to withstand fire from the ion canons dotted around the planet.
The Tollan are quickly forced to develop weapons that will pass through barriers (including the SGC's iris), until these weapons are destroyed by SG-1. This results in an all-out assault on Tollana, resulting in the almost total destruction of the planet.
This is a story that has not been revisited on-screen. In the expanded universe, a colony of Tollans survived and that is something that is not hard to believe, especially with their advanced tech. Their weapons may now be outdated, but there is a lot of other tech that could be used left.