Well yes, but the majority of it is captured by the middle class, in the form of public pensions, 401k's, the stock market etc.
See page 44 of the paper below.
You can look at Income, Wealth (net worth) or financial resources. Net Worth is probably the best estimate. You'll notice the top 1% has ~40% of the wealth. The next 4% have ~30% of the wealth.
So it would be very inaccurate to suggest that the "majority" of wealth and upside is accrued to the middle class, at least in the US.
"Household Wealth Trends in the United States, 1962 to 2016: Has Middle Class Wealth Recovered?" Edward N. Wolff
NBER Working Paper No. 24085 Issued in November 2017 https://www.nber.org/papers/w24085