Compellent's fate will be decided by politics, not by technology.
Jjust to straighten a few things out.
3PAR Adaptive Optimization Tiering is between CPG's,
so you could intra-flash tier between the CPG of 480 GB SSD and the CPG of 7.6 TB SSD and the CPG of 3.84 TB SSD.
Or even between RAID 10 SSD and RAID 50 SSD.
I don't think it make sense to move data between different types of SSD's,
but it is possible on a 3PAR.
And you can write to SSD first, then have Adaptive Optimization move data to lower tiers from there.
If Compellent All Flash or VNX All Flash is so fast, then why isn't there a public SPEC test showing something faster than the public SPEC test showing a 3PAR 8000 series doing 1 million IOPS at sub 1 ms, like the test ExtremeIO publishes?
Do a POC, and see for yourself why 3PAR is outselling Compellent and VNX.