The question then seems to be about the initial cost of hardware? i.e. Are we assuming that the limiting factor will be electricity when the limiting factor in the future may be the cost of hardware?
Cost of hardware influences your decision do you buy new mining hardware or not.
Once you have the hardware, the decision when you turn it off depends only on running costs. So, yes, the electricity will always be the limiting factor. There will always be some miners that run at the edge of profitability.