@mamaretti
What OSC library are you going to use, or are you going to write one yourself ?
If you intend to use ArdOSC currently no WiFi shield supports this library out-of-the-box.
ArdOSC uses some low level functions of the Ethernet library that "talk" directly to teh Wiznet W5100c chip on the Arduino Ethernet card. You'd have to rewrite that portion and adaptit to the specific hardware your WiFi shield uses.
If you are interested in an alternative solution I'll PM you so we don't hijack this thread 