Your question is very interesting. Vasp has just reported its willingness to sell 50% of LAB to Continental Airlines. There are no news regarding a possible bid or even a take-over. LAB was bought in 1997 for U$ 50 million.
TAN, from Argentina, is quite a small player in Argentina and it doesn't quite fit Vasp's current route network and strategy. If Vasp goes belly up, TAN is most likely to remain an independent airline, go broke or be absorbed by a larger Argentinian airline.
Ecuatoriana, which belongs to Vasp as well, is not doing that great. The current Ecuatorian financial crisis, bad management and increasing competition from AA in the MIA route are certainly digging the grave for this carrier. It is even possible that Ecuatoriana may go out of business before the parent company.
Pluna, Varig's airline in Uruguay, has vital links with its Brazilian parent airline. It is vital for Pluna that Varig improves its current performance, because Pluna's European and North-American services are all done by Varig through Sao Paulo, Rio de Janeiro and Salvador hubs. Discontinuations of any of these flights by the Brazilian government will have a negative impact in the Uruguain travel industry. This is pretty much the same sceario regarding TAM - Mercosur, TAM - Brazil and the Paraguay.
However, in the case of a possible merger between Brazil's Big Four, the world will see one of the most important strategically positioned airlines around, with services in Brazil, Uruguay, Argentina, Paraguay, Bolivia and Ecuator (not to mention the extensive code-share agreements they have everywhere). It would certainly not be the largest and well-managed carrier around, but it will surely be an interesting player for any major world alliance for its route network and virtual monopoly in key South-American markets.
The fastest way to become a millionaire in the airline business is to start as a billionaire.