https://en.m.wikipedia.org/wiki/Gauge_boson
(there might be a graviton, too)
With a Grand Unification Theory, they might turn out to be one force with several aspects (eg electroweak force), but that's not really a continuum.
There are phenomena explained by the particle model, and there are phenomena that are not. This is true of all models, and it's a a strong claim that we could eventually land on a "correct" model at all.
To be fair, a "particle" as the term is used in quantum field theory doesn't refer to a billiard ball, it's a perturbation in a "field" and encapsulates behaviour which could be described as wave or particle or neither.
The utility of a model is what it describes.
In my view, we're sailing awfully close to metaphysical waters with phrases like that.
That scale is the point at which we might gain some level of confidence that we know what "really" is a particle (or its constitution), whether it is truly a point particle or if it is just convenient to assume that at the present time.
Of course, the scales involved are far beyond anything we have been able to probe. And this arguement relies fundamentally on the interaction between gravity and quantum mechanics, even though those theories are famously not compatable. So the 'theoretically' in theoretically impossible is doing a lot of work.