I think that yes it will give a measurable performance boost to the petrol powered non-hybrid privateers, but will it allow the likes of Strakka and Rebellion to challenge the works teams? ... probably not.
The 'BoP' formula is fiendishly difficult to manage. The ACO (quite rightly) tinker very gently and infrequently with tank and restrictor sizes. The WEC committee may not be so circumspect. I sense an end-of-honeymoon period for the ACO-FIA joint venture is in prospect. If history is destined to repeat itself, expect Le Mans to drop off the WEC season in 2015 (if the series lasts that long).