In theory, shouldn't CM6 work on the Epic4G with minimal tweaking considering its advanced state on the Vibrant? (& Captivate?) Or is this round II of "CDMA and GSM phones with basically nothing in common besides the factory they came from"? I was under the impression that as long as you temporarily wrote off use of the 4G radio and could live with dysfunctional voicemail, text messaging, and tower-based location service (all of which would obviously break if you tried using them with apps meant for AT&T or T-Mobile), you could almost take the Vibrant's CM6 buildfile, tweak it a bit, and end up with a distro that would suck miserably and be dysfunctional on day zero (before you started porting the Sprint-specific stuff), but would basically boot into Android and be more or less capable of limping along as a phone (or would at least boot into Android, then crash and reboot the moment anything tried to touch the network).
I expect the Epic 4G to thrive nicely. Right now, the tools needed to port, customize, and reflash the rom itself are still being developed. If anything, the Epic4G scene is nothing short of miraculous compared to the Hero. From what I remember, the first custom ROM that was even *capable* of booting Android and limping around with little more than the ability to use the display, touchscreen, and wi-fi didn't show up until Thanksgiving, and the first custom ROM that was genuinely usable without sacrificing the camera & bluetooth didn't show up until after Christmas. By comparison, the Epic4G is moving along at light speed.
In the long run, we're lucky -- Samsung built ITS kernel using proper .ko loadable kernel modules, so we (hopefully) won't have to go through the BS that HTC owners do with driver support. It's not *guaranteed* that the .ko modules for the camera, GPS, etc will work on a Gingerbread-capable kernel... but unlike the Hero vis-a-vis 2.6.29, it's not guaranteed that they *won't* work, either.