I know people may jump on me for saying this but I have a hard time thinking any of the new colors will be collector pieces. I don't have a crystal ball so I know I could be wrong but I do know that these were made in much greater quantities than the older bags like eggplant and pumpkin. I think they were also made from different leather. Even now there are anthracite and VG bags on ebay. Last I saw there were three VG and two anthracites. I think bbags have more mass appeal now and the newer bbag lovers seem to go from color to color rather quickly (and because of forums like this, certain colors get hyped, people feel they need to buy them and then some also seem to move on rather quickly and sell them) so there is much greater turnover. The people who collect the old bags aren't buying many of the new so the old bags don't come available as often (or if they do, they fetch a higher price). I am not saying that the newer bags won't still get a good resale value but I don't think there is a high likelihood that they will ever be like eggplant or seafoam or a pebbled or a flat brass bag.
I am new to all this still, but I think it will take a few years for current season bags to be sought after, as the numbers dwindle. BUT, I think that Bbags will still tend to stay much more desirable and resellable than other bags, simply b/c the colors change every season and are never repeated. It almost adds this desperation to the hunt and helps you justify your purchase, b/c you know that you may not be able to find it again in a few months time. But take an LV bag, and you know they'll still be around in a year's time.