Yes but only when either a) they had new hardware to announce like last year's Mac Pro or, frankly, if there wasn't enough big news in the software side.
This year WWDC was entirely software driven with huge announcements across the board. Their two hour slot was so packed they were blasting by big new features in iOS with just a slide or two. Heck, they even dropped the usual 'here's how the company is doing along with a video of the latest Apple Store' opening. A spec bump iMac just wouldn't have made any sense in that context (and, indeed, would likely have generated negative headlines on the usual ludicrous 'Apple are doomed' lines).
Ultimately the PC industry currently finds itself in a slightly weird position as everyone is waiting on Intel. Broadwell is currently delayed thanks, it seems, to problems with the new 14nm manufacturing process and it's thrown schedules out of whack across the board. We're in the very weird situation of having new motherboards that support Broadwell on sale even though the CPU itself is still months away. As Broadwell is likely to bring significant power / heat improvements it's a reasonable assumption that new designs are built around those improvements so can't just be launched with the current Haswell processors. Hence most companies now putting out slightly speed-bumped versions of older equipment with any new features that they can get (in some cases thanks to being able to use the newer chipsets that should be going with Broadwell).
Actually, the reason they have started announcing hardware cause they pulled out of Macworld . And the reason they did not announce anything this year is cause they had nothing big, not cause the software was so awesome. Just look at WWDC post Macworld to see the hardware they have announced, it's quite major, iPhone 4 being the most impressive.