It's not an easy matter to make predictions about the stock market, since no one really knows what it will do from day to day or even year to year. (Over long periods, though, it has always gone up.)

Still, I'm here to make a prediction, and I'm predicting that three stocks in particular will be worth more than Costco Wholesale (COST 0.50%) a decade from now. Here's a look at those companies -- and at Costco too.

First off, why am I focusing on Costco? Don't I like it? Well, I do, and I'm a longtime shareholder. But arguably, the stock price has gotten ahead of itself at recent levels. Costco's forward-looking price-to-earnings (P/E) ratio, for example, was recently 50, well above its five-year average of 39. Its recent price-to-sales ratio was 1.53, above the five-year average of 1.08.

With 903 locations worldwide (623 in the U.S. and Puerto Rico) and a recent market value of $428 billion, it may be hard for Costco to grow at a rapid clip. Also, if a widely feared recession happens, maybe Costco will see some customers let their $65-per-year memberships lapse, as they fear spending too much at visits to Costco. (Costco does have lots of great prices, but it can be hard to not spend a lot there.)

Costco has averaged annual gains of around 20% over the past 10 and 15 years. Let's be a little conservative and estimate a 12% growth rate for the coming decade. That would put its market value at $1.3 trillion in a decade.