Sly 5. Technically it doesnt count because there wasnt an announcement, but the series ended on a cliffhanger with Sly 4 that never got resolved.

Sly Cooper was my whole childhood, man. Every passing year since 2016, I’ve lost hope a sequel is gonna come out at all. Especially considering how every Sly-related project has just been swept under the rug since then. But damn do I miss that series.