I think, if you have passthru devices, you have to reconfigure your machines but there is no problem about booting machines.
Also it's better to install fresh ESXi on second host and restore configuration on that.
The below links are useful for create backup and restore configuration:
You might find it advantageous to remove the VMs from inventory on your current host (so they stay on the iSCS datastore). Migrate your hardware, configure esxi, configure the iSCSI datastore and then import the VMs from the datastore. They are "just" files afterall.
Before I saw the first reply I went ahead and migrated everything over (didn't backup+restore config, just straight up moved everything over). ESXi booted, it retained static IP, retained datastores (which means it retained iSCSI/MPIO config) and VMs booted (they prompted me with that moved or copy question upon starting). So it looks like it does just work for the most part on identical hardware. I couldn't verify anything else (like the directpath/passthru stuff) as the host produced a PSOD (related to an isolated issue I'm currently troubleshooting, not this switcharoo/migration).