Extra hardware performance need not come at the expense of ease of programming.
And no, at the end of the day, people would likely go for the platform that provides better performance for the same price. In a console environment it's tickle down and not up. Xbox 360 and PS3 are very similar in performance but third party devs had problems with PS3 and to this day we keep seeing inferior ports compared to 360, so in effect your supposition that next gen more power will hurt MS is moot.
I insist, i think it's not.
And it's the other way round: more power won't hurt MS, it just won't give them much of an advantage. It's the other (2) system(s) turning out much less powerful that might be a limiting factor.
I think devs would rather work on less detailed, less demanding -in terms of development costs- assets, and just bump resolution, aa, fps or shaders on the more powerful system.
This is what's currently happening with PC games, they mostly give you a 'prettier current gen' experience despite the hardware being fully next gen, so to speak.
Having to develop a game so that it can be scaled down to run on less powerful hardware is a huge constraint and it might affect games' core structure itself, instead of just graphics, if the difference in CPU and ram is significant.
Which I don't think is going to be the case, however.
Extra hardware performance need not come at the expense of ease of programming.
And no, at the end of the day, people would likely go for the platform that provides better performance for the same price.
Yes, but that's not what I'm saying.
What I am saying is, if next gen gives you 3 systems, with one being considerably more powerful than the other 2, than its power is never going to be used to its full potential except from the few exclusives.
I'm not saying devs will rather work on ps4 assuming it's easier to develop for because it's less powerful (like you said, the opposite is more likely to happen). I'm saying they will, however, have to develop games with its (hypothetical) limitations in mind, since their game will need to run on that too.