It has not been discredited, yet. It has been challenged. You should see the latest paper on this subject that used gneetics - Characterizing the genetic differences between two distinct migrant groups from Indo-European and Dravidian speaking populations in India[1]
The study you point to seem to have flaws like comparing a very narrow set of group, driving to conclusions about colour tones etc. They try to punch hole in David Reich paper by saying the size per group was not significant, but this is flawed as the number of group was diversely large i.e 30 compared to 2 in this study. They do not try to point flaws in previous works as well. Read this article for the original set of studies that led to the discrediting of AIT http://www.newslaundry.com/2014/08/11/indiana-jones-and-the-...
No, most historians agree that the decline of the Harappan civilization and the arrival of the Aryans is separated by around 500 years.
The Aryan 'Invasion' Theory is one that was concocted by the British and is not actually based on any scientific evidence. The wide consesus now is that it was more of a slow migration than a invasion.
Regarding the linked paper, there is no concrete evidence that Harappan was a Dravidian language.
No. It's been challenged, and the characterized genetic differences between the two populations, while existing, does not point to any recent history signifying a cultural divide. This intermingling between the so called ANI ("Aryans"), and ASI ("Dravidians") genetic markers between the two population is not a recent phenomenon, and in fact at this point the two populations do not in any way point to a cultural difference as the time frame for the intermingling of these genetic traits predates much of the cultural connotations that "aryan", and "dravidian" denote, not to mention the very concepts are genetically irrelevant today, because of the intermingling that began around 4200 years ago making the two groups sharing a common genetic make up. [1]
The India of today is fundamentally uniform, and shares a common shared genetic makeup throughout all the tribes, castes, and geographies. So the idea that somehow these genetic differences point to a cultural divide is bunk, because fundamentally the cultural divid postdates the genetic intermingling. Furthermore that common shared genetic makeup is not a recent phenomenon, because the genetics of India has for the past 60,000 years been relatively the same. So whatever genetics that exists in India today, whether that's isolated, or mixed, has for the past 60,000 years been relatively the same. [2]
The R1a1a gene that's commonly referred to in these instances that drive the Aryan, and the Dravidian divide theory is a gene marker that points to a population that many argue proves the idea of Aryan invasion, or at least migration, as the R1a1a is a common genetic marker in Poles, Czechs, Lithuanians, and other Eastern European genetics, and not in India. That alone is a weak argument, as the question then is who had the gene first, and who migrated where. A closer, and higher resolution look at genetics gives a different picture. The Europeans carrier of the R1a1a gene have a further M458 mutation of the R1a1a gene that's virtually nonexistent in Asia. Since the M458 mutation is estimated to have occurred at least 8000 years ago it seems that something happened to divide the populations that carried the common R1a1a gene, but the reason of that divide is yet to be empirically established.
Thus this genetic marker explains at best a shared ancestry between Europeans, and Indians, not some Aryan invasion theory. The R1a1a genetic marker is not a common genetic trait among Europeans, west Iranians, or throughout central Asia, but found commonly in South Asia. [3]
So no. The Aryan invasion theory is thoroughly debunked as Imperial bias to subjugate, and justify their economic plunder over a people.
Thanks! This, along with the other replies, was very helpful.
So, basically the whole concept of North Vs South India divide with Southern Indians holding on to this information is incorrect since Indian subcontinent is pretty uniform for about 60,000 years.
[1] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4120727/