Bagless...
...Is a craze that will pass, IMHO. I am guessing that Dyson will retain a portion of the market, but I know an awful lot of people who have bought into the bagless thing and have sworn, "never again!"
What most people (not collectors and buffs, but the average person who's trying to keep a house clean) want is a vacuum cleaner that demands the very least amount of attention possible. Bagless cleaners cannot deliver that; if you don't keep up with filters and keep all sealing surfaces on the dust cup and its mount scrupulously clean, the thing is gonna leak dust. It's no damn fun at all emptying a dust cup, and by the time you've bought a replacement filter for a bagless, you could have bought all kinds of bags.
Bagged cleaners are just simpler for the masses and multitudes to deal with, and I'm betting they'll be back in force very soon. Bagless cleaners are sort of like stainless-front refrigerators, which are now encountering sales resistance, because a lot of people have had one, and don't ever want to try keeping one free of fingermarks and kitchen schmutz again.