Connect one (new/old) Xbee S2 to Xbee wi-fi using serially on UART pins. It should work well in AT mode, but for API mode you may or may not need to introduce a micro controller in between.
i was hoping that i can do the two operations (receive from xbee S2 and send to internet) on the same xbee chip, but it seems that it is not possible.
About your sugestions:
1- digi connect x2 is about 110$, so it is out of question
2 - since i’m using arduino on the coordinator side to receive data from the other S2 router modules, i’ll simply add a wifi xbee and use the arduino to bridge data from S2 to the internet.