The Tetete population in 1945 was estimated at around fifty people, perhaps involving only one or two extended patrilineal households. (p.434).
Their last contact with outsiders—an American Evangelical missionary and his Siona-Secoya translators—occurred in 1973 (p.422).
In March 1966, two Capuchin missionaries persuaded the [oil] exploration company to take them by helicopter to a temporary landing site nearby. They found their way into a Tetete settlement and spent five days with its three inhabitants: two men—one aged around fifty, the other around sixty—and an old woman.
Around 1970, an American Protestant missionary named Bruce Moore interviewed the three Tetete and confirmed that their language was closely related to Siona (Barriga López 1992: 185). In 1973, the same three Tetete were visited by Moore’s colleague Orville Johnson (who lived with the Siona-Secoya). This time Johnson brought three Siona-Secoya assistants; they learned that the survivors were siblings, still mourning the death of their eldest brother (p.433). By 1975, when Vickers took a census in the area, he counted only 266 Siona-Secoya and no Tetete (p.434).
Oil companies and missionaries are now accused of their extermination.

the language is possibly extinct today

No known speakers. Ethnic population: 3 (1969 SIL)
(Unchanged 2016.)