Seems to me that as everything is revolving or travelling on a curve, one day it'll all be heading back to where it started.

Isn't that exactly what is predicted?

If you want to think of the universe in linear terms then imagine  it expanding at the speed of light from a central point.  from any point in the universe nothing observable is travelling faster than the speed of light and light from an object in the universe moving at just less than right angles to the Earth would have been emitted just after the occurrence of the Big Bang.

Anything moving beyond a right angle to the Earth would not be observable as the light would never reach us.