The Internet is rife with new "Sherlock" season 4 casting rumors after fans spotted a Twitter exchange between series creator Mark Gatiss and "Outlander" star Sam Heughan.

On their social media accounts, Heughan greeted the series creator and actor for his birthday. Gatiss then replied and asked the Scottish actor when they will see each other. Heughan replied that they can catch up as soon as their schedules fit, but fans of "Sherlock" believed that the actor could be perfect to portray the role of Sherlock Holmes' (Benedict Cumberbatch) brother in the upcoming season.

However, both camps of Gatiss and Heughan remain silent about the possibility of the actor's appearance in the show for season 4.

Meanwhile, Cumberbatch continues to deny the rumors about the fate of "Sherlock" season 4 after previous reports quoted him saying that the upcoming season will be the last.

In an interview with BBC Radio Two's "The Chris Evans Breakfast Show," the actor claimed that he was misquoted in the GQ UK article. "This came from an arts desk or any kind of news outlet going, 'Oh we really need a story', so they sort of shipped out this quote which said that I said, 'This is the last one', which is not what I said," the actor stated in the interview as spotted by CarterMatt. "I said, 'For the time being'. And you'll see when you watch [the new, fourth season], that there's a good reason why I said that," he added.

Cumberbatch also mentioned that what he meant during the interview was there will not be a new season of "Sherlock" immediately after season 4. However, he also admitted that the people behind the series have a tendency to be unpredictable. This means that plans may change in the future.

At the moment, BBC has yet to reveal the official release date of "Sherlock" season 4. But it is expected to be released in 2017.