To calculate the maximum IOPS you can achieve with your current virtual environment (SAN and ESX host), here is a formula:
queue depth*(1/storage latency in ms)
Let say your queue depth is 64, your storage latency is 7ms, theoretically the maximum IOPS you can get is 64*(1/.007)=9142 IOPS
Not bad at all for a single VM, but if you have a big consolidation ratio, something like 15:1, this comes down to 609 IOPS per VM in a scenario where all 15 VMs use a constant load on the storage.
And 609 IOPS per VM can quickly become an issue for high IOPS demanding applications such SQL.
Thus upfront of any VMware implementation, carefully design your storage and use this formula to have a good idea of the IOPS you can expect.