We'll see how far the whole working from home thing goes, but there are a number of types of business for which it is impractical (e.g. anything that requires expensive or bulky equipment) and many people prefer to work together in person. As for co-working spaces...co-working spaces I've seen have offered offices and suites in addition to shared space. I worked out of a private office in one for a while because I wanted to use my own equipment and didn't want to schlep it in and out every day. That same reasoning applies to larger companies.

I'm aware that the big open office floorplans shared with 3 other companies is probably the only office environment that most HN'ers have worked in, but it's far from the norm. Most mature companies prefer to have actual private offices for their knowledge workers.