It starts to get weird for the manufacturer when customers use something then want to return it because something new has just come out. It's also weird for the customer to buy something, use it once or twice, then learn about the new version, like in your case.
The manufacturer doesn't want to kill sales of existing stock by pre-announcing the new version, unless his dealers were allowed to either discount the old ones to move them, or were allowed to return the unused old ones . . . in which case, what's the mfgr gonna do with them?
But a good designer is never satisfied. He's gonna keep tinkering and improving and sooner or later he'll have something he likes that he wants to introduce to the market.
If it's a significant break with the old design, like, say, a digital controller version while the old one is analog, and they can co-exist due to different price points, then that's not usually a problem. But an improved version that will be replacing an existing model always causes weirdnesses at release time.