It's not unusual for the R&D teams at the hardware manufactures to start thinking about the next generation within months after the release of the previous one's release. These things take years to put together, you know. I'd be more worried if Sony and Nintendo weren't thinking about their next platforms.
As for what form they take, now that is a very interesting question. It's inevitable that physical media will go away, possibly as soon as the next generation. Even in this generation, only the Wii U allows games to be played off of the discs. Both the XB1 and PS4 require installs which makes the discs little more than glorified product keys that ease the pain of having to download 45GB at once. Penetration of high speed broadband (>15Mbps) is really going to be critical for this to be a reality.
At some point, Nintendo/Sony/MSFT will have to decide if losing the market of people without fast enough connections is worth the savings of not having to manufacture and maintain disc inventory. I suppose there could always be some compromise solution with rewritable flash storage that could be downloaded and encrypted at retail (sort of modern take on the old blank SFC carts in Japan) for those without the bandwidth, but who knows. Either way, I don't expect retail to go anywhere since discoverability is still a pretty big problem with digital storefronts, and having flashy displays and download cards that can be purchased helps spread the word.
Now, what about cloud gaming? I think that this will become increasingly acceptable to the more casual segment of the market that wants a Netflix-like experience for games, and I think it could work great for certain genres that don't require fast responses, but for hardcore gamers for whom latency is dirty word, I'm not sure the the technical challenges will be solved to an acceptable level.
What's more likely to happen is that Nintendo/Sony/MSFT will continue to have their market share eaten into by Apple/Google/Amazon and there will be some breaking point where the traditional console manufacturers have to decide whether to chase larger less engaged audiences or vastly increase their tech and pricing and compete for the hardcore PC gamer who is willing to really invest. The next 10 years should be very interesting.