CNBC analyst Mike Santoli noted that the S&P 500 index remains on an upward path, institutional investors are fully invested, but market expectations for a rate hike at the Federal Reserve's next meeting are close to 50-50, and the 10-year U.S. Treasury yield approaching 4.8% remains a key concern. He believes that a key tech ETF indicator used by John Kolovos of Macro Risk Advisors, which combines investor sentiment and action data, could be a crucial signal for determining whether this bull market can continue.