The latest runtime updates are here: Update runtimes to support v3.4 (paths) · Issue #613 · EsotericSoftware/spine-runtimes · GitHub
The Java, C, C# and Actionscript3 runtimes are now at 3.4.
That means any third party engines using those should be able to take advantage of those already when they are ready.
The official engine runtimes relying on the above are also ready: XNA/Monogame, Unity, SFML, Cocos2dx and Starling support paths and linked meshes.
Spine-Unity in particular has had support for linked meshes for months now.