Investment expert Jeremy Siegel thinks investment returns should be OK, in this article (hat tip to Greg Mankiw). Siegel is an academic who really knows his stuff. Read the article carefully, but . . . take it with a grain of salt. Short-run investment returns are terribly hard to forecast. Even long-term returns are not easy, though there seems to be some reversion to the mean in 20-year performance trends. My advice continues to be have a good, diversified portfolio of assets, including stock investments and real estate investments.
(The traditional lore says also own bonds, but I have trouble accepting the low returns from bonds. Also, most folks have mortgages, and I don’t see a lot of diversification value in borrowing for one purpose, then lending for another. So your diversification strategy should involve paying off the mortgage, to at least stop being short bonds.