There will surely be more big-screen devices, but it is tough to imagine that a year from now Samsung will still be able to command the same high prices — the new phones are expected to cost anywhere from $700 to nearly $900 for the high-end Galaxy S6+. Even this year could be tough at those prices.
I think 2015 is the start of the shift, and 2016 will be the first year that we really see lower-cost "flagship" phones take over the Android market. The quality of the Moto X and Oneplus Two are right up there with Samsung, LG, and HTC's $600-900 phones at a fraction of the price. With all the major carriers shifting to a sane pricing model that ensures that customers know the full price of the phone's they're buying, the $200+ price difference is going to start to make more of an impact than ever before.
I have been thinking about this issue for some time, and think that the big Android makers are going to need to find clever ways to turn a profit because the high-margin phone business is fading fast.