Re: Use of MPLS
For SDN case I would say that, best case scenerio it can share the fate of IPv6.
For many years we have been talking about adress depletion, serving to other IPv6 enable host having IPv6 at the Internet edge at least or nowadys Internet of things so on.
Even we have very good use cases still most networks dont have it and We stress that best deployment scenario is Dual Stack.
So we can not assume IPv4 might go soon thus we are claming Dual Stack is the best among the others ( Tunnels, translation). So for SDN case since huge number of networks ( most SPs and large enterprises ) designed their network with MPLS and enabled many application of MPLS ( VPNs, Traffic Engineering, MPLS TP so on ), I would not say that once SDN comes things will change.
You may still need to bring new equipment to support Openflow/SDN, employee training, business requirements and many consideration needs to be taken into an account.