Well, the United flights (IAD/ORD) are generally pretty full, even at their high prices. With the combined United/Continental they will have direct service to ORD,IAD,IAH,EWR from Brazil with (eventually) flat bed business class on all flights.

Unless there is an increase in flight capacity from Brazil, I don't see United losing substantial business. Perhaps people will shift to TAM and book codeshares on United?