why not SANCopy, cut-over will be a simple matter of shutting down the host, running one final incremental copy, changing zoning and bringing up the system on new VNX.  When you setup initial SANCopy session you will set it up as incremental and then you can run incremental copy as many times as you like to keep it "close" to source.  SANCopy is very fast, i would strongly consider it versus deploying PowerPath on your all hosts at this point.
We have about 20 WS2008 failover clusters all running SQL we need to move to a new VNX. Currently the hosts use MPIO, no PowerPath in place. I've seen that PPME can do this according to bits and pieces on the forums, but is there an actual vetted process documented anywhere which allows these migrations to occur without lengthy downtime? Someone here also suggested Open Replicator or SAN Copy, but I don't see those as being a solution between VNXs. They can't afford much if any downtime, a reboot is about it apparently. Any direction greatly appreciated.  thanks
Migrating SQL clusters from VNX to VNX