Based on comments from Cisco representatives in the DMVPN/FlexVPN sessions at Cisco Live!, there's no plan to support DMVPN/FlexVPN on ASA. This may have changed since then, but I doubt it.
Infrastructure VPNs are slowly but surely moving away from the simple policy-based IPSec VPNs that the ASA supports to more modern and flexible route-based VPNs like DMVPN and FlexVPN. The key phrase here is "route-based", which puts the technology firmly into the purview of routers rather than security appliances.
The ASA units are very good at what they do, but modern infrastructure VPNs are just a bit beyond their scope.
