"Dragons love tacos. They love chicken tacos, beef tacos, great big tacos, and teeny tiny tacos. So if you want to lure a bunch of dragons to your party, you should definitely serve tacos. Buckets and buckets of tacos. Unfortunately, where there are tacos, there is also salsa. And if a dragon accidentally eats spicy salsa...oh, boy. You're in red-hot trouble. The award-winning team behind Those Darn Squirrels! has created an unforgettable, laugh-until-salsa-comes-out-of-your-nose tale of new friends and the perfect snack."
But, to the topic at hand, I think 5e will show longevity beyond 3e, 3.5e, and 4e. I would like to think that the next edition will just be a refinement rather than an overhaul. But for better or worse, editions are built into the long-term RPG model. Heck, even Warhammer Fantasy RPG, which originally touted that it would only ever have or need one edition, is going into #4.
That being said, I don’t think we’ll see 6e until the excitement for 5e fades. Which, so far, it shows no signs of doing so, and has only been growing.