SDN is horse shit
for anyone other that those ultra large service providers and massive enterprises.
It's all hype. You can google "techopsguys sdn" and the first link will go to my 4,300 in massive detail talk as to why SDN is over rated(I confirmed my suspicions with the person who created SDN which was what inspired the article). In a nutshell networking companies are trying to make L2/L3 networking exciting (it's not). They failed with DCB/DCE/FCoE 5-6 years ago and they are failing again with SDN today.
The network is not the bottleneck, I cover that in depth, obviously far more than I could include in a comment on el reg (especially because I can't have pictures and diagrams etc etc).
Maybe some day it will be for mere mortals, but by then it will be so automated you won't even know it's there. You won't have to "prepare" for it, it will just be there. No special training, no special products, it'll be basically be transparent and make the network easier to manage.
If you are not an ultra large enterprise or service provider and you think you need SDN, more likely you did an absolutely terrible job building your network.
I think that is still at least say 5 if not 10 years out.