Source: Apple.

Apple (AAPL -0.82%) is scheduled to report earnings on Monday, April 27, after the market closes. The iPhone is far and away the primary driver of the company's sales and earnings, so all eyes will be focused on performance for the new iPhone 6 and iPhone 6 Plus models.

Research firm Piper Jaffray has published a research note claiming that Apple is on track to crush revenue estimates on the back of stronger than expected iPhone 6 sales, both for the quarter ended in March and the rest of the year.

Wall Street analysts can make mistakes like anybody else: in fact, they often do. This means investors need to take these forecasts with a grain of salt and always do their own homework. On the other hand, we can often gain valuable and informative insights when analyzing reports from Wall Street firms.

Why the iPhone 6 could be different
Apple typically launches its new iPhone models in September, and demand tends to be particularly strong for the latest versions. This means iPhone sales are particularly vibrant in the fourth quarter of the calendar year, which is the first quarter of Apple's fiscal year, and demand tends to moderate in the following quarters.

Piper Jaffray believes the iPhone 6 is fundamentally different from previous iPhone models, as the larger screen means Apple will make big share gains in markets where consumers were previously more inclined toward Android devices.

According to the research firm, Wall Street on average expects Apple will achieve a 12.5% global smartphone market share during the 2016 calendar year, selling approximately 229.6 iPhones. However, Piper Jaffray believes Apple could actually grab a 14% market share, allowing the company to sell 258.1 million iPhones in 2016.

Under this assumption, Apple could beat sales forecasts for calendar 2016 by approximately 7.9%, and earnings per share could exceed the average forecast by $1.20.

Reasons for optimism
Sales numbers are always hard to predict with any precision, but Apple has achieved considerable market share gains lately, and this supports Piper Jaffray's thesis.

Based on estimates from Gartner, Apple surpassed Samsung as the top smartphone vendor in the world during the fourth quarter of 2014. Apple sold 74.8 million iPhones on a sell-through basis during the three-month period, which represented a whopping 49% increase from the same quarter in 2013 and put Apple in a leadership position with 20.4% of the global market.

Samsung came close with 19.9% of the market. However, the South Korean company's quarterly smartphone sales fell by 12% to 73 million from 83.3 million units in the final quarter of 2013. While the difference in market share between Apple and Samsung is quite small, the trend clearly favors Apple.

According to a research report from Counterpoint, Apple is making big inroads in key Asian markets such as China, Japan, and South Korea thanks to the popularity of the company's latest iPhone models:

Apple's iPhone volumes grew across key countries with timely global roll out of flagship iPhone 6 & iPhone 6 Plus models and also helped by relatively lower priced iPhone 5s & 5c, targeting prepaid users in emerging markets. Japan, Korea, and China were the bright spots where Apple registered a higher than expected demand for its newer and bigger display sporting iPhone 6 & 6 Plus models.

China will most likely be one of the main growth epicenters in the smartphone industry in coming years, and the Apple brand is enormously popular there. According to the Credit Suisse Research Institute's Emerging Consumer Survey, Apple is one of the leading brands when it comes to purchase intentions in emerging markets, particularly in China, where the company beats the competition on purchase intentions in both handsets and PCs.

Only time will tell for certain if Apple will beat sales expectations in the coming quarters. One thing looks clear, though: The company seems to be gaining market share versus the competition, especially in high-growth emerging markets, and this is good news for Apple investors.