If Sprint is pushing the Nexus like crazy now (5/23) that means that people who buy it now have until 6/23 to decide if they want an E3D.
More than likely, most people who got the Nexus are likely to be happy with the Nexus, unless they have technical problems. It's still shiny/new.
I like a previous poster's theory of Sprint having to wait XX amount of days between a phone releasing and a phone release date announcement. I'd actually like to put an addendum to that. It doesn't make any business sense to do that, anyways. While I don't think the E3D necessarily makes the Nexus obsolete, it certainly could be seen as counter-productive to release a phone and then immediately release something that could be seen as better immediately after it. Sprint invests money into the phone R/D. That'd be like throwing away money. So, instead of letting the Nexus be overshadowed by E3D, they're doing a media blitz to try to promote the underdog, then rolling out their heavy hitter in a sudden fury.
And maybe they're also taking a page out of Apple's playbook. No, not the play where you say the users are holding it wrong, but keeping hush-hush about it and then suddenly say...here it is!