U.S. stock futures are declining as investors return from the Christmas holiday, indicating potential pressure on the markets when they reopen. Futures tied to major indexes, including the S&P 500 (represented by $SPY), Nasdaq 100 ($QQQ), and the volatility index ($VIX), have all shown a downward trend. Reports suggest that the Dow Jones futures are also operating lower, reflecting a cautious sentiment among investors as trading resumes after the holiday break.