In the Lord of the Rings and The Hobbit, dwarves play a fairly central role: They drive the entire plot of The Hobbit, and much of Fellowship is centered upon Moria, the dwarven stronghold.
We see scattered references to dwarven kingdoms still existing, yet nowhere in the trilogy does anyone consider calling upon the dwarves for aid.
In the movie, Gimli is seen first with 2-3 other dwarves at the council of Elrond, who are not referenced again (at least in the movies).
He fully expects to find his cousin and other kin alive and well at Moria, even though they've been dead for quite some time (it takes a LONG time to decompose to purely skeletal remains, especially when you're locked away in a mine with a constant temperature and no elements to contend with). This indicates that communication between dwarven kingdoms is infrequent, months or perhaps years without news is not unexpected.
Gathering this all together, then:
- Lots of dwarves die in the trilogy and the prequel.
- No one even discusses calling upon the dwarves for aid against Sauron.
- The dwarves don't communicate with each other frequently.
- Gimli is seen to NOT return to his people after the trilogy.
This indicates to me that Gimli is, if not the last, one of a very small number of remaining dwarves.
Did Tolkien ever discuss this?