RFC4864 does provide alternatives for NAT in some cases, however there are gaps. As Brian mentioned in an earlier response, these GAPS could be solved in different ways, and while NAT66 may be one of them, there could be other solutions out there not being investigated. My prefered way of moving fwd is to first understand the actual problem that needs to be solved (problem space), then understand the solution space. Now, it seems the other way around, which makes little sense.
This makes sense to me, lets first identify the problems we want to solve and then see how to fix them rather than assigning NAT as a solution to problems that are not clearly defined. Eric