If you look at the 1st and 2nd generation of video game consoles starting with the Magnavox Odyssey in 1972, video gaming has a history of big names in the consumer electronics testing out the console waters. History shows a big name like Apple or Google entering into the market as very likely.
Personally, I think if Apple or Google comes in alone then a Sony/Microsoft partnership or a combination of Apple or Google pairing with either or both Sony or Microsoft is highly likely.
Microsoft in regards to Google and Apple has the advantage of culture, language, and a very similar, silicon valley business type. Sony's advantage is their multi-product line making any entry and exit for either Google or Apple less costly because Sony can eat the costs somewhere else down the line.
Nintendo I just don't see pairing because they have never needed to and the strength of their 1st party franchises are the best in the industry.
