Apple's latest announcements from its Worldwide Developers Conference in San Francisco could spell trouble for Facebook, RiskReversal's Dan Nathan said on CNBC's "Fast Money" on Tuesday.

Apple unveiled a wide range of software upgrades this week that will roll out along with its new iOS 8 mobile operating system this fall. Some of the biggest changes involve a revamp of the company's iMessage service, which will now include features like instant video and audio messaging, changes to group messages and location tagging.

So how does Facebook play into the equation?

Apple's iMessage updates share many similarities with Facebook-owned WhatsApp, which the company bought for $19 billion in February of 2014. While WhatsApp is available on multiple platforms, including iPhone, Android and Blackberry, Apple is seemingly making a play at many of the app's core customers.

WhatsApp co-founder and CEO Jan Koum quickly noticed the similarities between the iMessage updates and WhatsApp's key traits. On Monday, Koum sarcastically tweeted that it was "very flattering to see Apple 'borrow' numerous WhatsApp features into iMessage in iOS 8 #innovation."

According to Dan Nathan, Koum and Facebook may have good reason to worry. "I think iOS users who have WhatsApp, I think when this comes out, they're slowly going to drop WhatsApp," he said on Tuesday's episode of "Fast Money."

Nathan also said that if Apple ever chooses to license the software to Android, WhatsApp and Facebook could feel even more pain. "That could really make the purchase price of $19 billion look absolutely silly … I think we're going to see a $5-7 billion write-down (by Facebook) in the next few years."