This is the issue that Microsoft needs to overcome through marketing and crafting their message carefully. They can absolutely advertise it as two things in one, and depending on their price point can make a convincing argument for purchasing it as an entertainment system. There are more than a few people who have a PS4 because it plays blue rays, and gives them access to things like Netflix.
The Xbox 360 and PS3 currently have a ton of non-gaming centric capabilities, and the Wii U has a number of non-gaming centric capabilities as well (IIRC it has a quasi DVR feature). As far as we know, the PS4 is going to carry these features over and then bump up the social media element, and we can only assume there will be other non-gaming centric features as well.
It's rare that people use every feature of a product they purchase. I've yet to use my PS3 as a blue ray player, but it has that capability. I don't think I've ever participated in online play on my PS2, but it has the capability. My phone has dozens of built in features I've never taken advantage of, and thousands more that I could take advantage of with apps, but don't do so. That doesn't make any of these products a bad purchase for me, because I found enough value in the features I will/do use to justify the purchase of them.