People with good sources at Apple are saying there will be no iOS 5 preview this April and no iPhone 5 in June and that might be so. However, many of the reasons being giving to support this idea are just... nebulous at best.
First, they aren't "delays". You can't delay something that's never been announced. We've already gone over why Apple not announcing hardware in the WWDC press release is meaningless -- they never have announced hardware in WWDC press releases but have never-the-less shown off the new iPhone there ever since 2007.
There's been some talk that with the Verizon iPhone launch, Apple doesn't need "another" launch so soon this year. However, the Verizon iPhone launch was US only. For the rest of the world -- and make no mistake, Apple sells globally -- the Verizon iPhone launch was very literally a non-event.
A white iPhone 4 launch would be international but would also be for existing hardware -- hardware originally announced in June 2010. It will make some buzz and get some sales, but it probably won't provide significant enough momentum to really place-hold a June iPhone 5 launch.
What strategic reason could Apple have to delay iPhone 5? They aren't waiting on LTE anymore than they waited on a Retina Display to release iPad 2. LTE is primarily a US-only, Verizon-only story and nothing to risk tens of millions of international unit sales on. Is there a feeling nothing besides LTE is "big" enough for an iPhone 5 bump? I'd argue an A5 chipset (2x performance, 9x graphics) is as significant as the bump from iPhone 3G to iPhone 3GS. Add in a 4-inch screen, HSPA+ radio (which would have wider support than LTE), metal back, etc. and Apple could easily release that in June as a much more impressive update. (Just don't call it iPhone 4S.)
Would breaking with their past June release schedule change things up and keep the competition off balance? Maybe -- if they released earlier than June. Releasing later doesn't seem to provide as big a disruption, not when Android devices are already shipping or about to ship with NFC, dual-core chipsets (and built-in espresso makers for all I know...)
Same with iOS 5. Citing the "preview the future of OS X and iOS" line as an indicator we won't get an April iOS 5 preview this year the way we got an April iOS 4 preview last year. (Because it will only be previewed at WWDC). However, Mac OS X Lion has already been previewed -- has already been released in beta in fact. If OS X can be previewed before the WWDC "preview" then certainly so can iOS.
Apple could release this fall or they could release next year. They could be whispering that now to re-set expectations, or even just to throw said competition off guard. Apple could release iPhone 5 and iOS 5 at the September iPod + iTunes event but why would they? What advantage does it give them?
[Thanks to Phil Nickinson for the video suggestion!]