what happened to the kumans?

Lazlar�n Kuman T�rklerini torunlar� oldu�una inan�l�r. Ve "K�p�ak ve Kuman ayn� �eydir" diye duymu�tum.

Lazs are believed to be the grandsons of Kuman Turks. And I have heard that Kuman is the synonym of K�p�ak.

Actually I think it's the oldest western dialect.  I'm sure the oldest dialect all around is probably one of the ones spoken in Siberia.  They have had less influence on their language than any other Turks, I think.

Cumans were a privilegized group in Medieval Hungary under the direct authority of the King and the Count Palatine (dominus cumanorum). Later this privilegium was common with the iranian j�szok and ceased to exist only in 1853. I suppose the last people in Hungary who could speak cuman language as mother tongue were died in the begining of the XX. century.

Temujin:

I have no claim on this issue ,but I think you made a mistake.Volga Bulghars are ancestors of Chuvash not Tatars. Check your sources

Temujin I don't know chuvash  or Qipchaq and I'm not a linguistic at all, I just copy my sources:

This is britanica: (chuvash)

The Chuvash speak a Turkic language and claim to be descended from the Bolgars who in the 4th century AD migrated from Central Asia to the region west of the Volga River. It is not unlikely that they representan amalgamation of Bolgars with the tribes then living in the area. Theirlanguage is very different from other Turkic languages.

and this is (chuvash language) :

Chuvash constitutes a separate and distinct branch of the Turkic languages that differs considerably from the so-called Common Turkic languages; it is the only modern descendant of the extinct Volga-Bolgarian language. Formerly, scholars considered Chuvash to be a Turkicized Finno-Ugric (Uralic) language or an intermediary branch between Turkic and Mongolian. The distinct character of Chuvash is also indicated by its lack of mutual intelligibility with the other Turkic languages.

This is Encarta: (chuvashia)

Between 10th and 15th centuries,Intermariage between a local finno-ugric population and turkic-speaking Volga-Bulgarian Tribesof south produced the ancestors of the chuvash people.