Expanding-ring conjecture for the post-singularity set

Let $T_*$ be the singularity time and let $(r,x_3)$ be axisymmetric coordinates. Define

$$\mathcal{S}(t)=\{(r,x_3)=(\delta(t),0)\}.$$

Expanding-ring conjecture. The singular set of the solutions of the cited self-similar Euler construction propagates within the natural symmetry class as the expanding ring $\mathcal{S}(t)$, where $\delta(T_*)=0$ and $\delta$ is increasing in $t$ for every $t\geq T_*$. The statement concerns the continuation of the singular set after blow-up and remains open.