Backwards compatibility may be a factor in how well the next generation console do, at least at first. Their biggest competitors right out of the gate will be the last gen of consoles. For the Wii U it was the 360 and PS3. And for the new consoles it will be each other, the Wii U and the last generation of console. So to ship a console with out backwards compatibility in some form may be a negative factor to their sales after the initial adopter surge.
Because when most customers go shopping next winter shopping season, they will be looking for the most bang for their buck. So the cheaper consoles with larger libraries will immediately gain more sales then the new systems.
The problem with a Gaikai based solution is 1) you have have to more than likely pay for it, and it will be viewed as an extra cost and 2) It will suffer from NIntendo VC syndrom. Not all titles will be immediatly available, some titles will never be available, and on top of that you have to factor in the customer's bandwidth and data caps which may work against Sony. Not all people live in an area where there is adaquate bandwidth available and when it is it will have to compete with other services that may be in use. I know that I cannot stream with my service when there are two other instances of stream services active.
