Going up or down: there is more supply, so prices go down wrt. a situation without wind turbines, at least momentarily until the wind drops down indeed when we go back to a system w/o wind.
If you can store the energy, your energy cost goes down (but storage is not free of course, though getting cheaper).
Amortizing the fixed cost will mean the 'fossil' power is more expensive per kWh indeed, making it more and more attractive to buy storage as to bridge the gap between windy/sunny periods that do have cheaper electricity.
Some electricity markets have or a re looking at capacity mechanisms, they pay simply to have the capacity to generate power at any given time, even if not generating, eg. to be a backup. Eventually, that will be the business case for any fuel-powered power plant I suppose
