2050??? No need to step so far into future. Who knows how the race goes on in 2014/2015?
Best case would be that some kind of saturation accurs and difficulty turns into linear growth but that's very optimistical. I agree it's sad that one needs quite a lot of GH/s for reasonable mining.
Not at all, if the miner is cheap and power effecient, you can mine profitably very long. I waiting for 2014 if the miners will be cheap finally, so far very expensive for small piece of hardware...
Why will the miners be cheap? Any reason for it?
Miners will have their price based on the cost of manufacturing and also on the return they can get.
I see no reasons right now for cheap miners with 25000usd reward every 10 minutes.