Unfortunately, no physically reasonable detector could ever detect gravitons.  For example, a detector with the mass of Jupiter placed in close orbit around a neutron star would only be expected to observe one graviton every 10 years (see the below paper). The few that would be detected would be indistinguishable from the background 'noise', i.e. neutrinos.

See here:

http://arxiv.org/abs/gr-qc/0601043

Even though we can't detect individual gravitons, gravitational wave detectors may shed some light on them, since the graviton is the quantum of the gravitational wave (similar to how early 20th century physicists studied the nature of the photon based on properties of light, such as the photoelectric effect.).

What is the likelihood of ever discovering the graviton?
I've seen "determine" used for two completely different meanings:

Zeus' mood will determine tomorrow's weather. (determine = control, dictate)

The weather forecaster will determine tomorrow's weather. (determine = forecast, predict)

Are these meanings used equally often, or is one much more common than the other?
