Many do not know this but: all manufacturers share their new vacuums with each other. Several years ago, I took a group of collector friends to the 'vaults' at Tacony's engineering department. Rows upon rows of new cleaners. Most without serial numbers, as they were never for sale, and sent before they were launched to the public.
Working for a major manufacturer, and having helped with the design of the three new models coming from Tacony this year, I can say with total certainty that it takes as long as two years to prep a new model for launch. From design, to field testing of the prototypes, to ordering the VERY expensive tooling for injection molding, to the Marketing Department's long process of preparing photos and brochures, then sales has to weigh in on 'how' it's going to be sold, then boxing has to be created and drop and stress testing done, as well as life testing. It's a long, drawn out process.
The Generation Three was actually in life testing in people's homes while the Legend was being sold as the new cleaner.
Many years ago, when I was President of the VCCC, we went to Filter Queen's headquarters as well as Kirby. At Filter Queen, we saw the prototype of the Dyson-designed Filter Queen Cyclonic. At Kirby, John Lochner (head of engineering) took us into the Engineering Room and demonstrated what will be the Avalier to our group. The G5 had just come into production at that time. Mike Pletcher took some great shots of myself and Clay Floyd using the Avalier.