Sony probably isn't going to win America over Microsoft next generation. Halo sells about 7-8 million units there, while the PS3's biggest American game only sold 3 million there - a huge difference. The PS4 is going to need a franchise that can compete with Halo (or hope that Halo dies down). Unfortunately, at the moment, there's nothing that suggests Sony has the ability to make such a title. Or, instead of one big 7-8 million-selling game, they could try and push several games that sell 4-6 million units in NA each, but that still seems unlikely.
Sony should really try to go after Europe next generation. They have two franchises bigger than anything Microsoft has in Europe - Uncharted and Gran Turismo. These last few years have shown that the Playstation brand is still bigger than the Xbox brand in Europe. If Sony plays there cards right, they could expand the lead they had this generation. They need a good price, get Uncharted and Gran Turismo out early, and hope for a new IP to blow up. Perhaps their lead in Europe could even surpass the Xbox's lead in America.