Ok, to be honest I don’t know without experimenting. Yes, sure it can do that. But will it be at stakes with your time constrains, that’s the point.
Let me explain a little more how GMT plotting works. It uses what we call the PostScript layer cake model. That is, successive plotting commands append to the same PS file. When finished we “close” the postscript and call ghostscript to render the PS in the desired raster format (or PDF). While this is a fast process (seconds or less), depending on the figure complexity, the gs rasterization may take a while (or not).
Since you want to (continuously) update a figure, there are tricks one may do to make a copy of the (non closed) previous PS version, append a new layer, save it for next round, close it, rasterize and display.
So, yes it will work. But in due time? Well only experimenting with tell.