According to the original cast and crew of the trilogy, another sequel (fourth film in the series) is "highly unlikely" due to the cast changing in terms of age and voice. Dog Days has been described as the third and final (last) live-action film in the Diary of a Wimpy Kid film franchise. The possibility of a fourth film in the series, the sequel to Dog Days (and the Last Straw) is slim but not 100% denied. In August 2012, while doing press for the film, Jeff Kinney, Zachary Gordon and Robert Capron each indicated that there were no plans for a fourth film, (it wasn't in production, hasn't even been planned yet) but did not dismiss the possibility entirely. Kinney replied to inquiries regarding the possibility of another sequel, stating, "At present, we dont have a fourth film in development, but you never know!"
And when describing the likelihood of starring in another film in the series, Gordon explained, "[Dog Days] most likely will be the last movie. The main problem is [the cast] is getting older. You can't stop it. There's no way to temporarily stop us from changing and growing up. You know, that's the problem because the characters are supposed to be timeless." In March 2013, Zachary Gordon stated in a Spreecast live stream that there would not be a fourth live-action film. Jeff Kinney has indicated that instead of doing a live-action film of the sixth novel Cabin Fever, he would like to see it adapted into an animated film, stating in an interview, "I hope that it gets made into an animated movie. I'd really like to see it turn into an animated television special"
As of November 2015, It's been over 3 years since the third movie came out in August 2012, and the trilogy has had a pretty regular production of making one movie annually (every year) by having the first film in March 2010, the sequel and second movie in March 2011 and the third movie in 2012, so the creators would be breaking the "every-year" trend by not making a fourth film in 3 years (as of 2015). Zachary Gordon, the actor for the main character, is 17 years old now. Unless if the director and producers wouldn't mind making a fourth film with a much older high-schooler version of the main character that ultimately skips over the transitional gap between the main character in the third movie (an 8th grader) and the main character in a next possible movie (12th grader) we might expect another film. However, looking at the circumstances above, it would be highly unlikely that they will be making another sequel movie, unless if it's a reboot with an entirely different cast and crew. Similar to Home Alone 3 where there was a different cast. So it is still possible to have another sequel but with a different, younger cast. Jeff Kinney already mentioned that a 4th movie based on The Long Haul was under high consideration at 20th Century Fox. Corey Fogelmanis should play Greg Heffley in the 4th Diary of a Wimpy Kid movie (The Ugly Truth) and Zachary Gordon can maybe have a cameo appearance as Greg's older (future) version in Greg's imagination.