[Galaxy S 4 Q&A, Help & Troubleshooting] BarryH_GEG:
You kind of have to put the SGS4's sales "decline" in context:

High-end smartphone sales are slowing. Primarily because the market has matured and penetration is now high. This is an issue that affects every high-end smartphone manufacturer equally. And in emerging markets high-end phones aren’t what sell. As an example, high-end smartphones over $400 USD only made up 2.5% of smartphone sales in India in 2012. Phones between $100-130 USD were 30% of sales.

Samsung may have outpaced Apple in smartphone sales last quarter, but it’s facing the same slowdown risks as its biggest competitor. Both companies are battling to dominate the world’s smartphone market. In places such as the United States, nearly everyone who’s interested in buying a smartphone already has one, decreasing demand overall. But the smartphone revolution has yet to hit the world’s most lucrative markets such as China and India in full force. That leaves smartphone companies in a bind. High-end devices provide the lion’s share of smartphone profits, and are still too expensive to appeal to customers outside of the major cities in the world’s most important markets.

Samsung, overall, is well-positioned to navigate this split. The company is already the market leader in China and picking up more customers across the globe, thanks to its strategy of offering a wide range of devices apart from its premium iPhone competitor, the Galaxy S 4. Apple, meanwhile, offers older versions of its phones at lower prices rather than specifically making cheaper phones.​

http://articles.washingtonpost.com/...one-market-smartphone-sales-smartphone-makers

The SGS3 sold 50MM units over twelve months. Analysts have lowered their estimates on SGS4's shipped; primarily because of the above. But in this example the analyst dropped his estimate from 80MM to 60MM this year. Since the SGS4 launched in April that allows for nine selling months. On an annualized basis 60MM is equal to 80MM SGS4's a year. That's a 33% increase over the SGS3's annualized selling rate.

JPMorgan now expects Suwon, South Korea-based Samsung’s shipments of the S4 to be 60 million this year, compared with a previous estimate of 80 million. Samsung sold 10 million units of the S4 within 27 days, the company said.​

http://www.bloomberg.com/news/2013-...pmorgan-cuts-estimates-on-s4-seoul-mover.html

Samsung itself never disclosed actual SGS4 sales targets for 2013. All the numbers being talked about were unofficial analysts estimates. In terms of overall mobile sales revenue Samsung will probably still meet analysts’ expectations. This year Samsung's got a ton of products launching in the same time frame (SGS4, SGS4 Active, SGS4 Zoom, SGS4 Mini, Mega, N3, a bunch of mid-range phones, and four new tablets). The concern becomes "profit" rather than "sales" because Samsung makes less on non-Flagship devices. Here's what Samsung's CEO said about the SGS4's sales.

"I can say sales of the Galaxy S4 smartphone are fine. It’s been selling well. The report (by JPMorgan) was based on its own analysis. Probably, the bank may have corrected its previous bullish estimate about the S4 sales."​

http://www.gsmarena.com/samsung_ceo_says_galaxy_s4_sales_are_fine-news-6210.php

Samsung, because of their dominance, has become like Apple. They are the company the investment community and media "love to hate." A headline like "Samsung loses $20B of market value" gets a lot more clicks than "HTC reports another disappointing quarter." So at every opportunity expect to see some tidbit regarding Samsung's performance to become "major news." They and Apple generate 95% of mobile device profits. There may be fewer profits because of changes in the market place but the 95% of profits they both share isn't going to change. And if Apple and Samsung are "challenged" where does that leave the dozen manufacturers sharing 5% of mobile device profit?