Per the CCIE team, CCIE Routing & Switching Version 4 lab seats are now at 100% capacity:

The last day to take the CCIE Routing and Switching Lab exam v4.0 is June 3, 2014. Presently, all of the lab exam seats for the v4.0 lab exam are filled through the June 3rd last day to test date. Since the original announcement was made, there has been a tremendous number of candidates that have scheduled this lab exam. To meet the demand, Cisco increased capacity as much as possible, yet the demand for lab exam seats continues to exceed the number of available lab exam seats.

If you do not have a seat to take the v4.0 lab exam, you will not be able to schedule one, and the support team is no longer able to help you to get a seat. Please do not open a case through the support tool. We recommend that you focus on preparing for and taking the CCIE Routing and Switching Lab exam v5.0.

In other words, stop refreshing the lab scheduler 1000 times a day and stop crossing your fingers that you'll still be able to book an RSv4 lab seat ;)

For those of you that were originally planning on taking the lab exam in the v4 format, but are now faced with the v5 format, I would encourage you to attend our  CCIE RSv4 to RSv5 Transition Technologies Class coming up on On May 9th & 10th, 2014.