IPv6 in Azure VNET is currently previewing globally- in ALL Azure Public cloud regions.
Announcement (Service Update): https://azure.microsoft.com/en-us/updates/public-preview-microsoft-adds-full-ipv6-support-for-azure-vnets/
Links to Documentation & Samples
Full documentation including sample scripts is available here: https://aka.ms/IPv6ForAzureVNETdoc
A sample JSON template is posted in the quickstart repository: https://azure.microsoft.com/en-us/resources/templates/ipv6-in-vnet/Chris Launey commented
You can't peer VNets that have overlapping IP (v4) ranges, but if we every VNet could be assigned a unique IPv6 CIDR block and then the VNet network constructs supported them, that would support lots of use cases:
* infrastructure VNet to support other VNets with infra/support services, Azure ADDS, etc.
* B2B connectivity with VNets of partners whose network ranges might overlap with yours
* direct connectivity from Azure to private data center or other cloud services to support hybrid / multi-cloud strategies