If current technology had enough resolution, scientists would have scanned the planets already for oxygen, methane and water (which mixed together don't quite exist unless there's a continuous force, like life, unbalancing the physical reaction).
I realise they would have done this already if they could. I was thinking more in the medium term - the next 3-5 years?
Actually, they have. There are observations with the Spitzer space telescope infrared spectrograph of planets occulting their star, where if I'm not mistaken one could see something like methane absorption signatures of the atmosphere of the planets. That's not very surprising, since these are Jupiter-like planets and they have methane clouds in their atmosphere.