Interesting, I recall reading somewhere that
Osgiliath was
never rebuilt and that
Minas Tirith remained the capital. Maybe in the appendices? I don't have a copy of any
books at the moment.
Ingwe, about what you were saying, the rebuilding of the bridge; I agree fully that
bridges are one of the most important pieces of infrastructure to rebuild, especially as
Gondor's
realm would spread and settlers would doubtless begin to move east. The
Easterlings would not remain hostile forever surely and trade eastward would be necessary. However, that doesn't mean that 1) the bridge would be in Osgiliath - why not at
Cair Andros? or 2) that the
city would be rebuilt around it - though logical to rebuild it around any transport route
Tolkien may have had reasons for leaving the city ruined or even 3) that Tolkien agreed with our logic, for he may easily have decided that trade east would not benefit Gondor, and while he may have been incorrect in this his word is sort of final.
Of course, we don't have anything definite, which is why until a quote floats to the surface to prove that Osgiliath remained desolate I shall side with Ingwe.