An implication of the question is what will happen in the future. I will assume the earths interior will cool with time chaning the continental drifting. With slowing drifting mountain building will decrease so that denudation will likely be dominating. A problem here is that we probably need to consider loss of atmosphere and other issues that we do not know much about. There are indictions from Mars that water has been more abundant in teh past yet the topography on Mars is significant because the erosional processes have lost their poser as loss of water may have been critical.

So what will happen in the futiure depends on how tectonic and atmospheric processes change in the distant future due to changes or development in both the earth's interior and the atmosphere in terms of water content (water being a critical componete in both weathering of rocks abnd transport of material in topgraphic terrain).

To conclude, the question is much larger than can first be thought and we need to consider large time frames in which many of existing processes and systems will drastically change. So to provide a time frame is very difficult and essentially pointless.