Hasn't it been more than a decade since any third party lenses have been made incompatible?
And even if Canon were to try something like that again, these lenses are all designed with upgradable firmware now.
OOPS, it just did. A whole host of Sigma lenses were incorrectly reverse engineered and have issues on the T6i. Sigma is offering to fix the ones still in production, but any older ones that won't work are just throwaways.