spx/gold is a way to measure the value of stocks compared to real commodity metal instead of printable dollars.
Gold is a "safe haven" for many reasons including that once its in your hand you own it and no one is your counterparty. Dollars depend on the federal reserve and the supply of dollars circulating. When you hold gold, you hold a real commodity that has tradable value that should rise over time as more dollars are printed to fund the government debt mountain.
Gold has two ways to win, 1. inflation, 2. demand for safety.
1.If the Fed choose to create some inflation to allow the fed to burn down the US national debt, then gold should in theory become more popular as a dollar hedge. Geopolitical stress might also help this inflation or high spending case and support the case for dollar hedges like gold.
2.If instead of inflation, a sell off or deflationary correction, we might see demand for cash and safety assets as the herd of investors seek safety all at the same time. Marketcaps are too large for all the cash and gold that is available, so again this case should also help gold and safe haven assets.
Keep an eye on the spx to gold ratio along with the other indices in gold terms to see which way history plays out.