For me I do not really see the point in 2.5 and 5. Either 1Gbps or 10Gbps etc. Otherwise interoperability between vendors and models becomes hard.
From what I understand these standards have been created more or less for wireless. Listen to Cisco a while back and the biggest problem today is users are more and more wireless. That creates a issue for Acces Points that only use 1 Gbit at the moment. For a Enterprise to change all cable’s to something that supports 10 Gbit + access points with 10 Gbit is going to be expensive. 2,5 and 5 Gbit should be able to run and the cable’s you have and allows for more bandwidth to access points.
This is, according to Cisco, the driving force behind these standards and I would agree with them The biggest issue we have right now is wireless users + Skype with audio and video calls. QoS and 2,5 or 5 Gbit will solve this for us. QoS and 1 Gbit won’t cut it as the QoS will impact the main users to much.