Kepler-452b has one advantage going for it - the exoplanet was discovered using the transit method. Which should make the spectroscopy of Kepler-452b much more likely. Exoplanet atmospheres would be extremely difficult to discern if they did not transit in front of their parent star. We would have to wait until the James Webb Space Telescope came on-line in late 2018.I would be surprised, the planet is far away, small and next to a relatively bright star. On the other hand, I'm surprised by science frequently...
E-ELT is under construction, spectroscopy of exoplanet atmospheres is one of the main science goals.