The migration and settlement history of East Asia has been mired in confusion for a long time due to the complex interactions that have gone on over tens of thousands of years. Archaeological evidence has been sparse until more recent times and linguistic studies have lagged much behind Indo-European studies, due to a variety of reasons. However, recently (last 10 years, basically), genome sequencing has provided a much clearer picture of the principal East Asian migration routes between out-of-Africa and the written record. Some literature (below) now try to combine all the evidence, and it may be reasonable to put forward a rough diagram of what they suggest. By doing so, one reaches a conclusion similar to this article published in China. Notice that the Sino-Tibetan speakers (in blue) have ultimately displaced the first wave (in red) within most regions of China in the last 3000 years.

http://www.jstor.org/stable/3623130

http://www.cell.com/current-biology/abstract/S0960-9822(09)02067-3

http://jbiol.com/content/8/2/18

http://www.ncbi.nlm.nih.gov/pubmed/15173934

http://www.genetics.org/cgi/content/full/172/4/2431

http://www.springerlink.com/content/8dkq1943nr0xrmp3/

http://dx.doi.org/10.1016/j.humimm.2007.02.006

http://www.ncbi.nlm.nih.gov/pubmed/17149388?dopt=Abstract