Hypotheses that cannot be sufficiently tested
Bose-Einstein condensation was predicted in 1924 and only actually seen in 1995. 

Gravitational waves were predicted by Einstein in 1916. It was proved that they followed from general relativity in 1958. They were observed indirectly in 1974, and observed directly in 2015.

If "science" had been restricted to hypotheses which could be tested in the near future with available methods, then these predictions would not have been considered science, and it would have set physics back by decades. 

I would agree that hypotheses which cannot be tested in principle are unscientific.