We expect to move all current physical builders over to GCE in July, when they roll out KVM support.This means we'll use about 150 additional GCE builders.

We currently have about 200 free IP addresses, but given the long lead time for requesting them, we should request an additional block well in advance of needing them.

See these:
  go/cros-gce-bots
  go/cros-builder-address-whitelisting