Some of the managers in charge are concerned that as this is a relatively new feature of SQL server, and Microsoft may cease to support it.
One interpretation of this concern is related to literal deprecation and / or removal of the feature. The existing answer covers that very well.
Another interpretation is that, despite the feature continuing to live on, it may be "abandoned" and not improved significantly in future versions of SQL Server.
Consider columnstore indexes, introduced in SQL Server 2012. This feature had serious limitations in the initial release. But each new version of SQL Server since then has expanded the feature significantly - removing restrictions, adding new capabilities, new monitoring DMVs, etc.
On the other hand, something like SQLCLR has seen comparatively little innovation (or adoption!) since it's initial release in SQL Server 2005.
Is there a roadmap to this feature that says what Microsoft intends to do with this feature in the future?
Not explicitly, but one way to gauge whether a feature is not abandoned is by seeing if it gets development attention in subsequent releases. In the two major releases since 2016, there have been some improvements to temporal tables:
- SQL Server 2017
- introduced the "Retention policy" option, which cleans up old rows in the history table
- removed the restriction around
ON DELETE CASCADE and
ON UPDATE CASCADE referenced here
- SQL Server 2019
It's also important to consider interoperability with new features. For instance, temporal tables are not compatible with the new node and edge tables introduced in SQL Server 2017. So that's kind of a strike against temporal tables in terms of being "abandoned."
Are these concerns justified?
All in all, I agree that it's very unlikely this feature will be removed or deprecated. But if you're hoping to see the restrictions and limitations list shrink, it doesn't seem likely - at least, not based on the two major releases since V1 of the feature.