SEGA is nowhere near making any returns. They havent even made a return in terms of software, much less hardware.
Sony will bankrupt is the most likely scenario, at wich point their gaming division is probably not in much imediate danger, but it will be on long term.
Nintendo has made money every year, except last year wich they took a loss with to make the 3DS a sucess. It worked so its more money heading their way. Nintendo is in no danger of having to go third party.
If they failed that hard on home consoles they could always stick to the 3DS, but they sold the most last gen so i dont see that happening.







