How far away would we be able to detect habitable planets in, say, 2150?

And at what distance are we going to get details on them? From what I've seen with our progress in remote imaging, it seems to me that in a hundred to a hundred and fifty years (assuming we don't experience a technological collapse of DOOOOOOOM) we'll be well able to get pictures of planets with continental detail in other solar systems. But I don't have a good idea of how distant those solar systems could be; I'm sure we could (if they existed) get pictures of fair-sized islands on a planet around Alpha Centauri by that time period, but what about something 10 LY away? 50? 100? How far away will something have to be for us to know only roughly "there are planets there, and we think there's an oxygen atmosphere around this one, but we've got few other details."?