It's happened to me a couple of times, and both times I just stayed with the previous edition until something better came along.
The first time happened in the late 1980s...can't remember the exact year. My friends and I were playing the Basic and Expert boxed sets, and saving up to get our hands on the Companion rules when TSR announced their new edition. We were just teenagers at the time, and we couldn't afford to drop everything and pick up all-new books...assuming I could even find them in the evangelical small-town USA where I grew up. A couple of the wealthier upper-classmen had gotten their hands on some of the books, but it was largely inaccessible for me and my gang of friends. So we stayed with BECM, collecting the books from used bookstores, trading with other classmates, and photocopying pages to share with my friends (I had a student job in the library). And even when we were finally old enough to have cars and jobs and spending money, my gaming group wasn't really interested in re-learning a completely new gaming system for no apparent reason other than product availability. The only AD&D 2E books I ever bought were the "Desert of Desolation" series of adventure modules, and I bought them for $1 apiece at a garage sale and promptly spliced them to my "Master of the Desert Nomads" campaign.
So I stayed with BECM all through high school and college, until I moved away in 2000. I was no longer in college so I had a lot more free time. I had a whole new gaming group, too, and we used the new 3rd Edition rules (and later, the revised 3.5 Edition). It would be the longest-running D&D system I've used so far.
When 4th Edition was announced, my gaming group (now my third, and current, long-term gaming group) tried a few games but we didn't care for it. I don't want to ignite anyone's tempers or kick off another ENWorld Edition War, so I won't go into detail. I'll just say that 4E wasn't what we expected, and wasn't what we were looking for, and leave it at that. We thought Pathfinder might be a better fit, so I traded away my 4E books, and I bought all of my friends a copy of the Pathfinder Core Rulebook for Christmas.
But Pathfinder wasn't what we were looking for either...after one short-lived campaign where I tried to run them through the Serpent's Skill adventure path, we switched as quickly as we could to the brand-new 5th Edition rules. The 3.5E/PF rules were just too dense and fiddly for us...we were trying to play a game about heroes and magic, but kept getting interrupted with algebra homework and hours-long combat minigames.
And we've been with 5E ever since. The group is aware of the OneD&D playtests, and it's getting a lot of pushback from my friends, but we haven't made any decision as a group just yet. If we end up skipping it, so be it...it's a familiar road.