We do have other templates that support VM3+J3.x, such as: LightMart and CleanMart. Updates for SportMart and StyleMart are coming in 2 weeks.
Not very people are using CoolMart, so it is demand <-> supply. CoolMart does not have the top priority right now, unfortunately. It will be one the last ones that is going to be updated. I am not saying "never", i am saying i don't know yet, we are focusing other templates for now. I can't give you ETA, right now because this depends on the time-schedule, we have to stick with it. For instance, I am spending time here replying your message and trying to convince you; instead of working on testing the SportMart for VM3, which must be released in 1 week according to our schedule. If we can't release the new version for SportMart, we can't work on other templates, right?
Let me remind you something, "free update" subscription comes with 6-months. So, high likely your free update subscriptions have expired for CoolMart, and you need to pay the "upgrade" fee when is available. Furthermore, the "upgrade" won't be smooth, because "MANY" things have changed between J2.5 -> J3.x and VM2.5 - > VM3.x, you will have to start from scratch for each website that you want to upgrade. This is not because of CoolMart, this is because of the nature of Joomla -- there are migration tools for upgrading, but they don't work as expected in Virtuemart+Joomla websites. So, i would recommend you to take a look at our SportMart, StyleMart, LightMart or CleanMart.
Regards.