Hi, Antonio,
I’m Edgar from Accusys.
Just as what Bob said, there’s no Thunderbolt SAN switch so far.
But, we have developed a SAN solution for Thunderbolt units share the capacity of one set of storages (See the diagram below).

We have a Thunderbolt to PCIe converter to connect Macs to our switch; and make the Macs access PCIe storage. It is not purely via Thunderbolt connection, but it provides you the sharing capability.
You can view the slides on SlideShare to see the introduction of this solution.
1PB Shared Thunderbolt Storage
Or you can view this webinar video:
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If you are interested in this solution, you may contact me for more details.
–Edgar (edgar.chang@h3platform.com)