The chart below shows the (common) upward slope to the SPX implied vol termstructure. The same is shown for the TLT, a near mirror image, and downward sloping.
Inverted termstructures, like inverted yield curves, don't last for that long. They are associated with high levels of realized vol, which fund the purchase of gamma, most prominent in short-dated options. In plainer terms, inverted termstructures reflect disequilibrium. All of the major macro vol events have featured curve inversions. The process of finding equilibrium is about normalizing and disinverting that curve.
Second chart shows just how joined at the hip the SPX and TLT are. The second chart suggests that the first chart should look different. By this account, either TLT vol is too high or SPX vol is too low. That spread ought to narrow. I'd argue that things getting worse for the bond market could be at a tipping point of making things considerably worse for the SPX.