The ZSTAGE is on the accelerated list:
https://orders.decware.com/list_view_accelerated.phpI'm not sure how long the wait is, but it is much shorter than 4 1/2 years (and counting) if you were to order a e.g. CSP3 or ZTPRE.
As for the anniversary mods, they are upgrades to the power supply that improve the overall performance, esp. the speed and transparency of the component.