I'm sure the sales from ATS will act as a stimulate for SCS, and they might be able to get a few things done a bit quicker, but it's up in the air as to how long it would take to drive from coast to coast. I'm willing to bet someone's map mod will get there before SCS does, like what Promods did with Scandinavia.
Till then I'm going to keep throwing money at their DLC's lol