Sony phones have arguably been the best in the business when it comes to battery management, and as long as they have not sacrificed battery life ("2-day battery") it is difficult to criticize 4K as a "marketing ploy." As it is, their phones last longer than competitors' per charge. Viewed in that regard, 4K is purely a bonus without downside. Of course we can do the "what if.." thing, but I think that is rather pointless considering the cut-throat nature in this market segment. Besides, Sony offer 1080p phone and 720p in the Z5 family, meaning they are not removing options for consumers. I think they should be commended.
But Triluminous display technology has some problematic shortcomings for smartphones. The issues that I am seeing on Z5 are exactly the same kinds that pervade the past Z Series phones so I am not optimistic that they will be limited to pre-production units.