On the one hand, the W3C has this listed under new features for SVG 2.0:
"Allowed <paint> values and marker properties to take the child keyword and <child-selector> values to support ID-less referencing."[1]
That would mean you could have multiple inline SVGs on the same web page and avoid potential nameclashes from gradients and/or patterns having the same id.
On the other hand, that same page lists mesh gradients as a feature of SVG 2.0. I vaguely remember on the SVG archive that the browser vendors said they weren't going to implement that.
