Col. Enfield.
I would suggest there will be folks very interested in 50 years, as long as there is not a complete collapse of western civilization like that Rome saw. Fact is that with the Snider-Enfield the only major conflicts where it was "the arm" was the Abyssinian campaign of 1868, the search for doctor Livingston in the 1870s and as a secondary arm in the 1879 Zulu campaign. I guess also the 1886 upper Canadarevolt. Yawn...... It was a transitional arm without a lot of combat history.
Now compare that to the Martini Henry: with one major war the 1879 Zulu war and a few other secondary ones, 1882 Egyptian campaign, 1885 Khartoum relief, 1896~1898 Sudanese campaign (secondary arm), it still is an arm most Brit collectors want, and very few ever actually shoot. Still the demand for Martini-Henrys has always exceeded the supply in my period of collecting from 1982 to the present day.
The No1 MK III had a long Commonwealth history: WWI, the Irish revolution and civil war, Spanish civil war (secondary role), WWII, Korea, Mau Mau rebellion, Malaysian conflict (secondary role) Rhodesian conflict (police issue), Cadet use until the 1960s, Australianreserve and cadet use until 1968, along with being the dominate 100 yard finals rifle from 1920 to 1968 at any imperial match or meet. Add to that all of the Non UK
conflicts it was used in, such as the 1947 separation crisis in India, the Sino-Indian war of 1962, the Goa intervention 1962, the 1965 Paki-Indian war, the 1971 Paki-Indian war, the 1979 to 1989 Russo-Afghan war, the 1995~2001 Nepal crisis, early use in the US-Taliban war of 2001 to ?? The fact is you have an active use by this arm in so many conflict that it is sure to be one of the most historic rifles ever with a nearly continuous 100 year use history.
Even if the west goes under, the use of this rifle by pretty much every group in southeast Asia and the middle east will keep it of interest to some folks.
With something like 13 million made and about 900,000 still in use in India, I expect in 50 years you will still be able to buy ammunition for it as well as parts, though by then they may be new made. Folks are still shooting reproductions of US civil war arms and while that market has stagnated, it still exists.