Looking at the specs for the new iPhone, it certainly isn't the phone for Global roamers who want 4G everywhere - it simply doesn't cover the bands.

That said - 3G seems fast enough for me on my iPhone 3GS and I feel the need for 4G for a smartphone may be overblown.... YMMV.

If I were new phone shopping, I'd be looking at an unlocked Galaxy 3 LTE model.