Cindy Ord/Getty ImagesMega-cap shares have led US indexes lower in the final days of 2024.Market experts blame rising nervousness as investors recalibrate expectations for 2025.While correction risk grows, the bull run is expected to keep going through next year.Investors, starved of a year-end rally, may need to brace for further bouts of disappointment as 2025 kicks off, market analysts say.After US indexes were catapulted to double-digit gains through 2024, momentum has sputtered in the final days of the year.