Hi buddy,
After 3Y, as it is right now, you will be starting your upgrade/typerating course - then you need 1 year on type after that, before you can request to go onto another aircraft type thats flying out of your base (eg. B744, A340).
That being said, these shiny new B777ER are arrive soon, and by the time you have served 3Y they will prob. be doing US bases on that. What chances you got to get one of those bases is a question that is impossible to answer at this stage... Or you could, after you have done your S/O time, transfer to the freighter (and start at the bottom of the freighter F/O payscale - and thats !!!!!).
An even better question is whether you will even wanna be with CX for that long...
As you might see from other threads.. Suggest you head for a job with one of the majors around your home territory.
Anyways good luck - whatever you choose.
Y