Seen this before.
This is the same as when IPMI came out, as a standard base of code, for management processors, whereby PC vendors could build on it, with their own extra functions (read: proprietary).
Or when BIOS became UEFI (you-eff-ee) - again, it was standard BIOS with any crap you'd like to bloat your PC with, thrown on top.
I see similarities here - so it will end up the same. For better or for worse.
While I appreciate the values of SDN (although many a LAN and security bod would raise an eyebrow at it), this is levelling a field that should not be, because manufacturer's choice of silicon, ports, bandwidth, packaging, whether they do east-west or north-south traffic and reducing latency is what it's all about. For example, Cisco likes ot protect its 'core' switches, so they continue to insist on north-west traffic, whereas integrated (converged) systems now all do east-west traffic, such as Lenovo's PureFlex, and they're all better for it!
This would surely make the network vendors indistinguishable from each other, until they reach a high enough point in the hardware's spec, when you start noticing 'innovation' and 'uniqueness'. I'm not sure they'd willingly agree to wiping half of their margins, just so vendors from another market can benefit.