Pure conjecture. But I think there are many examples: look at dying empires, corporations, etc... its all the same. They stop seeing challenges, get lazy, and are taken over by some hungrier and scrappier entity. When the real challenge comes they're unprepared.

Do you think AGI will get lazy?

A program is neither lazy nor motivated. It does precisely what it is programmed to do.

I would push back on the question, as well as a myriad of implied premises behind it...

A machine learning model is not a program, is not programmed, and research on emergent motivation in ML models disagrees with this position.