Ultimately the Earth is going to look like Mars and be in the orbit that Mars is in today. The Earth is cooling and becoming less dense as it moves away from the Sun over time.

Meanwhile the sun is decaying the Earth, turning it into desert. The Sun is turning the earth and its atmosphere into less dense matter, and as a result, in order to move to its proper density area it moves away from the Sun's core in an outward direction.

It takes a while for this to happen, a long while.