What happens when the earth's inclination changes?

First of all, in your main question, you asked "when" so let me point out that the inclination of the Earth's axis to it's orbit around the sun does not change over time.  We do experience precession (where the axis points at a different place in the sky over time) and also Nutation (which is a wobble as it moves around through precession), but during both of these processes the angle remains roughly 23.5 degrees.  By the way, the fact that we have a moon as large as we do is the main stabilizing factor in keeping the earth at 23.5 degrees inclination.

Now, if it were to change, it would have global consequences.  If it shallowed, we would have less difference between the seasons.  If it increased, we would have much more pronounced seasons.  Either way, the inhabitable areas of the earth would change significantly.  As a result, wind patterns would change, ocean currents (Thermohaline Circulation) would be altered, etc.

Earth would be a much different place if we were not at 23.5 degrees inclination!!

so, do you walk across train tracks when massive locomotives come rushing at you pulling hundreds of boxcars (probably filled with melamine-contaminated dog food), just on the slim likelihood that the train will suddenly (and instantaneously) stop?

no?

why not?

Don't you think something that massive could suddenly just... change?

funny... neither do i.

the Earth is MASSIVE... the Angular Momentum (so huge it deserves capitals) of the Earth is not gonna just flip-over.  Ever.