The micro-camper is bound to be a niche market but you do see various types around, especially popular with climbers/walkers, birdwatchers etc. Also I could see its role as an occasional camper in 'stealth' mode to overnight in car parks etc when travelling around. As with the full size Cali, I like being able to drive somewhere, jump straight into bed for a few hours without any tentage involved, and then jump straight up in the morning to do whatever I went for.
If I was younger, single and only had money/space for one vehicle, I could see a micro-camper as an interesting option. But it would have to be modular, ie be able to take out the beds etc to use it as a pure load-lugger when needed. I'd also want only a single-width bed, so I could still access my gear even with all the doors shut in bad weather or in stealth mode. And a pop-top to make it a bit more habitable and airy.