If my memory serves me correctly and history is any indication, I do believe that Samsung came out (for example) with the Note 2 smartphone first in Europe/Asia and then later on across the pond in the US/Canada side. I believe it had different specs such as available in 16/32/64 GB versions while the US ones only came in 16GB. The same may be for the Q. Proof of this is the specs are not fully spelled out on Samsung's' (US) webpage other than category, usage, color and dimensions. Everything else is missing. Hopefully my theory is wrong and both sides of the pond get a 8GB version along with the 4.
Regardless, Its not a matter of if Samsung will create a 8GB (or more) version of the Q, it's when. Could it be this year, or next as a replacement for the current Q.