In terms of driving housing prices up, I'd expect growth in the stock prices of the bigger companies to be a bigger deal. If Google's stock appreciates 20% (or Apple's, or Microsoft's, or a rising market helps lots of companies out 5%), that affects a much larger number of people with equity than does adding maybe 100 millionaires.

Especially if the main thing keeping a lot of people out of the market is raising a down payment, not affording the monthly mortgage. To make a down payment, you "only" need a few 100k, not millions. It's in reach for people receiving significant equity value from their employers along with strong salaries, you don't need to get boosted into the ultra-rich.