In my case, I recently applied and was given a $5000 CL...however it is not signature version as I was hoping
$5,000 credit lines are the main requirement for Visa Signatures, but also the banks want to see higher credit scores and higher incomes as well since Visa Signature/World MasterCard offers an expansion feature. So, let's say someone has a $5,000 Visa Signature credit line and they spend $7,000 in one month. Their minimum payment would be $2,100 (2% of $5,000 plus the $2,000 charged over the credit line). As studies have shown, people with a higher score are more likely to repay that. Generally speaking, most reward cards these days are moving to Visa Signature/World MasterCard because merchants have to pay the banks a higher interchange (swipe fee) for the higher level card. This helps with the cost of offering the reward. So most banks will try to find a reason to approve someone for the Signature/World.
I am sure if you called them they might consider an upgrade. Someone on MyFico is reporting that Chase began to report credit lines on their Signature and World cards as of 11/6/11 (depending on the cards cycle date; these changes will continue to start reporting through December) . So no reason not to have a Signature now. Plus the metallic/hologram Visa Signature/World MasterCard logos that Chase has been issuing are pretty sharp looking.