Hello Jamie,
Welcome to the Microsoft Q&A and thank you for posting your questions here.
I understand that you would like to know if there a roadmap for Analysis Services Linked Servers in Azure SQL Managed Instance.
As of now, Azure SQL Managed Instance (MI) supports linked servers, but only to SQL Server targets such as SQL Server, Azure SQL DB/MI, and Synapse SQL. Extending this capability to other data sources, including Analysis Services, is indeed on the roadmap. But there is no specific ETA or detailed roadmap publicly available for when this feature will be implemented.
So sorry to read that this limitation affects your decision to migrate. I will advise you keep an eye on updates from Microsoft, forums or feedback channels, which can help you stay informed about any progress on this feature. For more information: https://techcommunity.microsoft.com/t5/modernization-best-practices-and/using-heterogeneous-linked-servers-from-azure-sql-mi/ba-p/3074530
I hope this is helpful! Do not hesitate to let me know if you have any other questions.
Please don't forget to close up the thread here by upvoting and accept it as an answer if it is helpful.