Will the orbit of the planets around the sun ever change?
They always change, all the time. Right now they are changing, in the near future they will change, and in the distant future they will change. The orbits are not, when you look at them in detail, nice smooth ellipses. For example the eccentricity of the Earth’s obit changes mainly with a period of 413,000 years. Ultimately, the Solar System is stable in that none of the planets will collide with each other or be ejected from the system in the next few billion years. Beyond this, within five billion years or so Mars’s eccentricity may grow to around 0.2, such that it lies on an Earth-crossing orbit, leading to a potential collision. In the same timescale, Mercury’s eccentricity may grow even further, and a close encounter with Venus could theoretically eject it from the Solar System altogether or send it on a collision course with Venus or Earth. In about 7 or 8 billion years, as the Sun expands, it will swallow the planets Mercury and, most likely, Venus, and perhaps even Earth. So ..
