It was originally supposed to release back in 2015

It’s been almost a whole decade since the first game released, but once again the publisher of Dead Island is hinting that the game is still in development. In a Twitter post, Deep Silver told one disgruntled fan that they “wouldn’t be so sure” about the game being cancelled.
We wouldn't be so sure about that! 😉
— Official Deep Silver (@deepsilver) December 3, 2020
In the Twitter thread, which was originally about Gat Out of Hell being free on Games With Gold until December 15, one fan replied with “Dead Island 2?” to which Twitter user yronyy replied “Give up man. It’s not coming. Just move on to Dying Light lol”. In response to that, Deep Silver said “We wouldn’t be so sure about that!” later adding “we’re not quite ready to talk about the latest Dead Island just yet, but when we do, you’ll see it here.”
This isn’t the first time that Deep Silver have hinted about the long-awaited sequels continued development. Last year THQ Nordic, the parent company said that the game was still in development, and the publisher made the same claims back in 2017 and 2018 after the game moved to a third developer in 2016.