The potential of this control is not fully usable if it supports only C# as one of the most used languages today. Today it would make more sense to also support languages like JavaScript/TypeScript, Python or Java which are much more adopted then VB (which is clinically death). Of course one could implement the desired or needed language, but to be honest, this is out of reach for most developers in terms of complexity and time.
So, if IG wants to increase the usefulness or value of XamSyntaxEditor, adding support for the mentioned languages could help a lot.