Not if everything's at the same baud rate... think about it... for evry two bytes you're receiving, you'll transmit only one, therefore you're going to be building up a backlog of data at a rate of one byte every two milliseconds (based on your 4800 baud) and pretty soon you'll run out of buffer RAM. On top of that you'll need Hardware USART for each receive channel because you won't be able to have multiple software (SERIN, SERIN2) inputs because as the PIC is grabbing data from one, you'll be losing bits from the other.