Pic partly related.

So let's assume all the Orkz got their shit together, got under one banner/warboss and WAAAAAAAGH'd from the Eastern Fringe all the way to Terra. How far would they get? If they get to Terra, could they conquer/destroy it?

Let's assume this is limited to every Ork currently within the Imperium of Man's domain. They all meet at the Eastern Fringe and piledrive as long as they can all the way to Terra. They conquer/attack planets in their way, but don't hold them or go too far outside the road to Terra.