Hi Mark,
You can Follow the implementation of scatter charts in the following page (I believe you have already found it, but I am adding it here for anyone else): https://feedback.telerik.com/blazor/1410853-xy-scatter-chart-type.
Thus, I renamed this page to be about bubble charts, so each item can be kept separate and easily traceable.
As for a roadmap - you can find it here: https://www.telerik.com/support/whats-new/blazor-ui/roadmap. We are focusing on the components and features with the greatest impact on a suite, and we will definitely add more series types in the future.
On a side note, you may find the following article useful in case you would already be using jQuery widgets in Blazor: https://docs.telerik.com/blazor-ui/knowledge-base/jquery-kendo-in-blazor. Basically, you could use all the ASP.NET Core feature through the jQuery Kendo widgets, as they are, under the covers, the same thing. While not a native Blazor component like the UI for Blazor toolset, this can let you work with familiar tools and a single license.
Regards,
Marin Bratanov
Progress Telerik