Where I work (Oz) runway changes are normally a coordinated change between Tower and Approach and this will often be after Approach has advised pilots of the downwind component and ascertained if they can still accept the old runway or not. Occasionally, the wind change is drastic enough for an immediate change of runway to be required.
So, normal procedure is we agree on which arrival will be last to use the old runway. Aircraft for current runway keep their STAR (Our STARs continue to the instrument approach or all the way to the runway for visual approach).
Departures will use the current runway until the runway change. If they can't accept the downwind component they will have to wait til the runway change occurs. Arrivals have priority over departures.
Arrivals that can't accept the downwind will be given a new landing slot to the new runway and would normally be given a new STAR. If they are close in they will just be vectored to the new runway.
There are various criteria for deciding if a runway change is required. Some examples are: More than 5 Knots downwind; Any downwind on a wet runway.
Most jet pilots will happily accept 10KT downwind (and often considerably more on a dry runway) especially, if it means you keep your landing slot.
This is the basics only, there are a lot more variables in the decision.