I guess such a capability may arrive through the "GeoExt3" project,
though its future name may be ngGeo.
That may bring the "Javascript heavyweights" that Andreas mentioned,
both in terms of developers and frameworks 
Personally, I think ngGeo may be a great foundation for a client-side
UI for GeoServer. I'm sure ngGeo will start off with an agenda to
duplicate GeoExt: "what features do we need to provide to wrap/manage
an OL Chart". But a proportion of those features would also be
applicable to a GeoServer client. So, some up-front architectural
planning may produce a design that most efficiently meets both sets of
requirements.
Ian