Duolingo, Inc. (DUOL) could be a solid addition to your portfolio given a notable revision in the company's earnings estimates. While the stock has been gaining lately, the trend might continue since its earnings outlook is still improving.Analysts' growing optimism on the earnings prospects of this company is driving estimates higher, which should get reflected in its stock price. After all, empirical research shows a strong correlation between trends in earnings estimate revisions and near-term stock pric ...