Get ready for weaker returns in 2025 after huge stock gains in the last 2 years, Wharton professor Jeremy Siegel says

• The S&P 500 will see gains capped at 10% next year, Jeremy Siegel said.
• The Wharton professor expects large-cap tech shares could see flat returns in 2025.
• But undervalued small- and mid-cap stocks will rally, he said.

The S&P 500 will be running on fumes in 2025 after a scorching two-year rally, Jeremy Siegel told CNBC on Monday.