According to Android Central (by way of a Sprint employee playbook and rebate manual) the HTC EVO 3D will most likely be available with Sprint sometime during the 4th week in June. The site calculated this launch date after taking a look at an employee manual that included EVO 3D training near the end of June, and it seems that date has been confirmed by the rebate schedule.
This is around the time we anticipated the device, but is far later than Radio Shack's "rough launch date" of June 4th.
If you're interested in purchasing an EVO 3D, you might want to check out Radio Shack; the company is offering the phone on contract for $200 -- unless you're trading in an Evo 4G or Evo Shift 4G, in which case you'll get a $100 rebate.
And it looks like the phone will be coming with an unlocked bootloader. So there's that to look forward to, as well.
Of course this is all subject to change, but for now perhaps we have a bit clearer view of the timeline.