It's worth noting that this is a purely cosmetic issue, and a fairly minor one at that. Pictures still come out fine, which is arguably the most important thing, but it's still undesirable on a shiny new piece of expensive technology.
Bigger is better
The complaints seem to be focused purely on the iPhone 6, with the iPhone 6 Plus seemingly remaining unaffected and it's not clear how widespread a problem it is, but if your phone is affected you should be able to get it fixed or replaced.
While there has been no official response from Apple yet various redditors claim to have got either a new display or a whole new device when they brought it into an Apple Store and one poster who claims to be an Apple Store employee said that they don't know why the cameras shift, though presumably it's something that Apple is or will be looking into.
- You can't avoid manufacturing faults but you can keep your iPhone 6 protected with a case.