The RS is alive in the NX2 GT Fusion. The "AT" line changed with a nylon heelcup/highback but the RS is the same. The reason for the change in highback for the "AT" was the difference the last couple years between the RS and AT was pretty minimal really. It was primarily in the top panel going from Nylon to Carbon. With the power triangle inherent in all Flow bindings, that made very little difference. So to further distinguish between the two NX2 models they have the base NX2 a nylon heelcup/highback.
The AT's you have will genuinely be fine on EITHER board. Keep those.