Warren Buffett is legendary for his long-term buy and hold approach to investing and as a result, his buying and selling activity is closely watched by investors big and small. Obviously, there's no crystal ball that will tell all of us what his next move will be, but some of our top Motley Fool contributors think there are good reasons why he may sell these three stocks sooner, rather than later.

Dan Caplinger: Buffett tends to hold onto his stocks for a long time, so it's always hard to project what he might sell. However, Verizon (VZ -1.18%) has already reaped many of the benefits of its smart strategic moves since Buffett's 2014 purchase of the telecom, and now might be a good time for him to exit his small position based on industry conditions.

Verizon is a typical Buffett favorite, sporting relatively low growth, a high dividend yield of 4.5%, and having been out of favor when he purchased the stock. The company took on huge debt in order to finance the full takeover of its Verizon Wireless division, ending a joint venture that had siphoned away 45% of the unit's profits to Verizon's partner. Since then, the telecom has made incremental progress in paying down long-term debt, but it still remains a substantial overhang.

I can see two reasons Buffett could sell Verizon. First, the wireless industry is going through a price war that could become even more brutal in the long run, and that could hurt Verizon's profits. But perhaps more compelling is simply that Buffett might choose to concentrate his bets in the industry on rival AT&T, which pays an even higher dividend yield above 5%. Either way, a Verizon sale wouldn't be a bad move from Buffett.

SOURCE: SANOFI

Todd Campbell: No one knows what's going on inside Buffett's brain box and trying to speculate is likely a fool's errand, but if pressed, I'd say that Sanofi (NYSE: SNY) doesn't jibe with Buffett's long-term sock-it-away mantra.

Sure, Sanofi is a global drugmaker with a big exposure to a big and growing patient population (diabetes), but its top selling drug could face off against generics soon and in the past, Buffett has been more willing to make big bets on stocks outside of healthcare.

Sanofi's long-lasting insulin Lantus is a $7.1 billion per year blockbuster, but its patent has expired and well-heeled competitors like Eli Lilly (NYSE: LLY) are chomping at the bit to challenge it. Lilly's Lantus copy-cat has already launched in Europe and a FDA approval could be forthcoming. Given Lantus accounts for a quarter of Sanofi's sales, it would appear that there's a lot of risk associated with its revenue and therefore its stock price.

I also think this holding could end up out of Berkshire Hathaway's portfolio sooner rather than later because of its small size. Sanofi only makes up about $1.9 billion of the $100 billion plus fund and to me that suggests that its far from a core holding.

George Budwell: When buying a stock, Warren Buffett is known for taking a company's "economic moat" -- that is, its ability to protect long-term profits from would-be competitors -- under serious consideration. That's why I think Johnson & Johnson (JNJ -0.15%) might be one of the next stocks that Buffett decides to sell. 

J&J's recent growth trend has been fueled almost entirely by its pharmaceutical division, and therein lies the problem. Although J&J's global pharmaceutical sales grew by 4.2% in the fourth-quarter of 2015 -- when excluding the negative impacts of foreign exchange, the company's competitive positions in key markets like oncology, hepatitis C, and inflammatory diseases have been eroding over the last year.

In oncology, J&J's star prostate cancer drug, Zytiga, saw its international sales essentially flat line on an operation basis in 2015, likely reflecting the increasing market penetration of alternative therapies. That's especially bad news for J&J because Zytiga has been one of the company's top growth products in recent years. 

Making matters worse, sales of J&J's hepatitis C drug, Olysio, dropped by a staggering 86% last year due to the approval of Gilead Sciences' competing drug Harvoni. And the company's blockbuster anti-inflammatory medicine, Remicade is now facing the threat of cheaper generic versions known as "biosimilars" in both the EU and the U.S. . 

All told, J&J does sport a highly productive clinical pipeline that could erase some of these noteworthy gains made by rival drugmakers. However, Buffett tends to prefer companies with economic moats that look nearly unassailable -- and J&J no longer fits that description.