Erosion: What Happens to Mountains?

Mountains. Are they really indestructible? I have that answer, and it’s no. Erosion can change rivers, plateaus, anything! The question though, is what will happen in a million years? I will be talking about Pike’s Peak, a mountain in Colorado Springs. I think Pike’s Peak must have started as a flat surface, and then when magma comes out of the ground when plates are moving, the magma cools and then more will sit and cool on top of it. In a few million years, either Pike’s Peak will get bigger, or erosion will cause it to get smaller, or while erosion acts upon and it keeps getting bigger, they will act upon each other and maybe not move at all. I think it will just repeat itself over the next few million years. Everyone has a different theory, and that was my theory.