Google has pushed back the announcement of Android Key Lime Pie in order to give more time for manufacturers to prepare and give them some time to first push the Android 4.2.2 Jelly Bean to their devices.
Also, more evidence points out to no big Motorola unveilings at Google I/O 2013. Instead, Google is once again said to bring a 32GB 4G LTE version of its Nexus 4. The LTE Nexus 4 might sell for $349, while the 16GB Nexus 4 with no LTE support could get discounted to $299. This could mean the most basic 8 gig Nexus 4 will be phased out or could drop to $249. Interestingly, the same rumor says the new LTE Nexus 4 will come with a slightly redefined design.
As to that brand new Android 5.0 Key Lime Pie and the mysterious Google Motorola X phone, those are expected to appear only later on in the year.