I think there are still plenty of landraces left, just folks need to track em down.
I gave the last of my Colombian Black ad Ethiopian Highland beans to friends in Florida to reproduce, the lumbo Black has been grown out and pollination has been done, so those beans will be available soon, the Ethiopian next year.
I am starting the last of my pure Zamal soon, sadly my pure Durban Poison didn't germ, but I hope to obtain some seeds from Mexico and Belize shortly.
I've got Highland Oaxacan Gold (2 different phenos) and Malawi Gold mother plants, so the raw materials are still available, the problem is that Haze took a lot of resources to develop, over many years, and it's not easy to grow out the large numbers for selection that went into the Haze line, but I still think that new pure sativa lines are well worth working on, cos if you think about it, there is very little landrace sativa influence in the commercial genepool, all I can think of off the top of my head is the Mexican, Colombian, Thai etc in Haze, the Thai, Durban and Kerala that Sam also used, the Brazilian Shanti used in White Widow and the Durban that was worked for years to bceom power plant. That's not a lot at all.
In recent years some companies like ACE and Cannabiogen have introduced some fresh sativa blood, mostly south American, but I think there is a very real need to inject some fresh blood into what's become a pretty stagnant genepool.