DECs or not is decided based on cost, not happy/unhappy pilots.
My understanding is the failure rate for DECs in the past has been higher than new F/Os and upgrades. The additional expenses incurred because of this makes DECs not as cost effective as they would appear on the surface.
Whether the curent policy changes will be dictated by the latest cost/benefit anaysis by the company. With the company's best financial interests as the overriding factor, of course.