There would be certain constraints in making a map like that that was big enough for 16+ players. That one there is actually pretty small. Also, you should be careful in the use of the word 'fidelity' - that map appears to be faithful to what Hollywood imagines SE Asia looks like. As RS is mostly South and West Pacific you can expect rather different vegetation - mangroves, bamboo, coconut palms, kangaroo grass, bougainvillea etc...
However, I am pretty sure we will endeavour to generally match that in terms of look and, when godrays come out in the next iteration of UDK, I think we can aim, in certain respects, to beat it.
That waterfall is pretty fecking sweet, though - been taking that apart in the editor for a few evenings recently.