It depends upon which cloud technologies you are talking about.
MPLS has a long and proven track record in virtualising network topologies. The first MPLS RFC was published in 1999. Changing existing MPLS DC designs is expensive and time consuming.
In addition Cisco has only just released this week the first CCNA Cloud exam and so there will be a shortage of skilled staff with skills in the newer cloud technologies such as ACI and SDN. I was a bit surprised to see that no CCIE Cloud is being released.
I think that greenfield data centres will start to incorporate the newer cloud technologies, but still retain MPLS at the distribution and access tiers of the campus network.
