From what I understood Sony put on hold the development of OLED TV because of the economic conditions. Sony hasn' t been doing well in the market lately having huge loses for years. So they probably cut the team developing OLED, and kept some members specially those working the blue LED problem.
Samsung and LG are coming strong in this market. LG even promised a 'giant' 32" (81cm for non UK or US citizens) OLED TV in 2012
source. They did this to beat the 30" one that Samsung announce. I think that the Korreans are trying to steal the shine from the Japanese firms and each other.
The Sony Samsung venture probably refers to the sharing of Chinese manufacturing facilities and some sharing of tehnologies. I haven' t heard of a deal between them. LG on the other hand had ties with Philips and a Japanese company (don' t know which).
From what I know Chinese firms make some of the pieces: motherboard, transistors, tube. While other pieces: tuner, current regulating are made in Korrea or Japan (in Samsung that' s how the labels show). The TVs are assembled in: Polland (Samsung), Czech Rep (Sony and other Japanese firm), Hungary (both and LG).