Based on reports here, I don't think current owners are getting any priority any more -- it's all about reservation time and which batches they choose to produce first (i.e., body color and interior color). I was a line waiter (albeit, west coast), and have had a P3D+ on order for nearly two months now with zero movement.
So, I wouldn't get my hopes up, at least with respect to getting in on full the federal rebate. My estimate still allows as late as November, perilously close to the end of the year.
That said, delaying ordering is just going to delay delivery.