Ethernet is supposed to be AC coupled through transformers, so PoE which is DC doesn't (or shouldn't) affect non-PoE devices. The DC voltage is the same on both wires in a differential pair, so no DC current flows through the transformer's input coil either. PoE is extracted at the center tap of the transformer. If the designers of this new standard have any sense, they'll have done it the same way. So sorry, no fireworks today.
