You don’t need upstream support for all features; you can often implement them in older SVG techniques with namespaced extra data to help with editing. That’s how text wrapping has worked in Inkscape historically, though 1.0 is introducing support for the actual defined SVG functionality.

Not everything is possible this way; mesh gradients can’t be emulated in vectors, for example—though you could effectively implement a canvas-backed renderer for it to polyfill it; but a lot of functionality can be implemented without upstream support.