I think it's an interesting theory, but it's just conjecture at the moment. Sure, it's possible that having an inadequate OS is the cause for low sales, but we have no way to test it out. The Vita and the Wii U are the only consoles on a decline. But these consoles also have plenty of other problems known to harm sales. If the consoles fix those problems and still have low sales, then you can blame their OS. At the moment though, they do have those other problems, so we don't know which problems are directly harming sales.
With that said, it's probably best to trust history and assume these consoles are being harmed more by problems such as weak libraries, high price, etc. rather than assuming a radical change in the industry. Claiming that consumers demand a certain type of OS is just making untestable speculation. Even though we can't know for sure, I will say it's more likely that other problems are causing harm, rather than OS problems.
