Can some human groups evolve into new species?
Absolutely it is possible for the current human species to evolve in to two distinct species in the future. Barriers to reproduction, such as physical isolation, help the process along as it allows differences to accumulate. Gene flow allows hybridisation (not in a species to species sense, but sub-population to sub-population sense) which will impede the process of speciation because it allows genetic variation which is unique to one population to move to the other.

Differences occur between populations, which can lead to speciation, by the mechanisms of evolution - mutation, migration, drift, and selection. Different mutations occurring in sub-populations allows the two to become genetically incompatible, leading to speciation. Gene flow from a third population may make the first two too different to reproduce (see also ring species). Drift and selection may cause genetic variation which allows reproductive compatibility between two populations to be lost, further generating genetic differences. Selection in different directions (e.g. the environment of the two populations is very different) can hasten speciation, as seen in a classic Drosophila experiment.

Will the population you mention ever become a non-human/novel species? Who knows, but they are certainly interesting - as you've realised, their isolation by geographic barriers will help differences to accumulate between them and other human populations that could lead to speciation.

I suggest reading more about evolution and speciation here!