By the fourth season, Sczeszny will be a brilliant gk. Imo you should just buy an experienced gk that can keep up his form for another two and a half seasons or so. Definitely try looking at Shay Given (if you aren't using LFC MArshall's update, that is), he is a brilliant gk plus he's out of favour at Man City in most of my saves. Maybe try looking at Fiorentina's gks (Frey and the Polish guy), they are also very capable.
If you really want a great young gk that much, then Adler, Lloris, Viviano and even David de Gea are all very reliable.