As I have mentioned earlier, the earliest literary traditions in Tamil might have fossilized the language. In my opinion, it could be the closest to the Proto-South Dravidian that reached the region of Tamil Nadu. Indeed, the author mentions that,
This conservative nature of high Tamil(modern Tamil) aids the political construction of the popular belief that Tamil is the mother of all Dravidian languages, making Tamil and Proto-Dravidian coalesce.Probably, we can safely assume that Proto-Tulu and Proto-Kannada are in fact older than Proto-Tamil if you consider migration routes. But as I have mentioned earlier, Malayalees were in fact, Proto-Tuluvas, who lost their language because of Tamil dominance. The Tamil they adopted went on to grow into an independent language. Ergo, Malayalam is the youngest of the major South Dravidian languages. Therefore, the language tree of South Dravidian languages would hardly change.
A rather unfortunate fallout of this Tamil==Proto-Dravidian popular belief is the linguistic studies dealing with developing higher level language families.
Among the living languages, genetic relationship has been suggested with far-flung languages like Basque in Europe, Japanese in Asia and Wolof in Africa. Their comparison with Tamil, not with Proto-Dravidian (indicating the mistaken coalescence mentioned above in the scholarly world also), is methodologically faulty given the time scale of any possible relationship.
I wonder how much progress has been made after that article was written(2003). I also wonder if the sound changes v-> b were in fact b -> v. I mean Kannada, Tulu and Brahui(may be North Dravidian languages too) commonly show words starting with 'b'. Even my mother-tongue(the so-called dialect of Malayalam spoken in Kasaragod) show the words starting with 'b' and never 'v'.