Researchers say that the Welsh language will "thrive" and by 2300 two-thirds of the population could be Welsh speakers.
More than a third of the world's 7,000 languages are currently classified as endangered and more than half are expected to go extinct by 2100.
There are a number of strategies in place in those countries to boost the language.
The researchers have developed a model which can predict changes in proficiency levels over time and, ultimately, whether a given endangered language is on a long-term trajectory towards extinction or recovery.
The data, published by the Royal Society, compares Welsh and te reo Māori, the indigenous language of New Zealand, as a case study.
That shows that while Māori is on a pathway towards extinction, Welsh will "thrive in the long term".
The model is based on Welsh in Wales, where researchers say "significant development in bilingual and Welsh-medium education and the presence of the language throughout the public and private sectors have positively contributed to an increase in the number of Welsh speakers.
"The model predicts that the revitalisation efforts will be successful and, in the long term, Wales will have a majority of proficient Welsh language users."
It predicts after approximately 300 years 74% of the population in Wales would be "proficient speakers".
However, it warns that isn't a "quantitatively accurate prediction" as it includes everyone being able to learn at the same rate, "which in reality is not the case".
It also warns the next 50 to 100 years is "relatively fragile".
The Welsh Government's report on Welsh language use in Wales, in 2014, put 24% of the population as Welsh speakers and 11% as fluent.
There is also a strategy to create a million Welsh speakers by 2050.
The study has looked at strategies in place to increase the learning rate.
It says that the education system is "one of the most powerful levers available to government policy makers for the acquisition of an endangered language" and that "strategies targeting learning at schools are likely to have the highest potential benefits".
Jeremy Vine receives a Welsh language lesson:
Other things that governments can do is provide early childhood education in the other language, integrate the language into both primary and secondary integration, development the number and quality of teachers and invest in language-immersion education.
"These have all contributed to the nascent Welsh language revitalisation," it says.
"Other factors in the Welsh case include the availability of university-level and adult education; the struggle to achieve equal recognition and usage of Welsh in the public and institutional spheres; increases in Welsh publishing, broadcast and web media and software."
