An increase in supply relative to demand is never a bad thing for consumers.
What's left of OPEC will lower their prices if demand for their oil decreases. If it lowers prices to where shale can't be developed and brought to market for a profit then the industry will not stay in that business for long.
Or shalers selling oil to the US market could resort to machinations to keep prices high here so that development remains profitable. Kinda depends on whether conservatives can help make it happen or if liberals can prevent it.