Mesh shaders are already used by Nanite for larger triangles on hardware that supports them. WPO support is coming to Nanite which doesn’t conflict with the mesh shader support we have already.
If you are asking do we plan to exploit mesh shaders outside of Nanite I believe the answer currently is no. Instead we are going the opposite direction and trying to support everything in Nanite, bit by bit. That is a very long road so please don’t read into that as everything can be Nanite soon but that is the long term vision and where we are investing our resources.