After the novelty of the latest big cartridge wears off, the cartridges survive based on merit in the field. The 480 has a lot to offer the handgun hunter: good bullets, a big hole with deep penetration, and reasonable recoil built into sound guns that are configured for handgun hunting. The one big strike against it is that cheap cast bullets, as are available for the 44s and 45s, are not readily available, so the gun remains too expensive for most guys to shoot frequently. Another big strike against it is that it's in the same niche as the 44 magnum.
Do I think it will last? As long as handgun hunting remains popular, they should get a reasonable number of sales. But I don't know how many is enough to keep it alive.
While I've always liked and wanted a 480, I've not been able to justify it to myself because the 44 is so good.
It's hard to tell with cartridges. I wonder how the 45GAP is doing. Great idea, but it doesn't seem to have gained much popularity.