At the 2024 Chinese CPSE show, Canon displayed a prototype camera with a 250MP sensor and a new EOS R7 camera high-sensitivity extended firmware. I assume this is the same 250MP APS-H-size CMOS sensor Canon has been marketing/promoting for years – since 2015 (see product page):
Canon announced the development of a 250MP APS-H-size CMOS sensor (29.2 x 20.2 mm, 19,580 x 12,600 pixels). Back in 2010 Canon made noise with a 120MP CMOS APS-H sensor. Full press release: