"1 what's the requirement of the collapsed distribution/core layer,i noticed that the full line rate is one requirement ,but is there some others? "
I wouldn't agree there's always a need for collapsed distribution/core device to support full line rate. I.e. device's performance capability should correspond with expected traffic load.
Other requirements might include things to avoid failure (such as dual power supplies) and a feature set to support functions commonly performed at both distribtion and core levels.
"2 what's the difference between 4928-10G and ME4924-10G,they are exactly same form factor. "
At the hardware level, I see the fomer's switch capacity is listed as 96 Gbps and the latter's as 48 Gbps. But I would suspect more differences at the IOS level. For instance, the latter's Enterprise Image notes support for AppleTalk and IPX, the former doesn't.
"3 3560E is also full line rate,can 3560E take the same role as 4928-10G in the collapsed distribution/core?why? "
It might but again the IOS feature set might be different. For basic L2/L3 switching/routing differences might not be important.
"4 why 4928-10G's ports are all fiber?why copper port is not used here? "
My guess would be probably some combination of Cisco expectation that most initial 10 gig runs would be fiber and/or product design before/concurrent with Cat6a. The 10 gig ports do support copper using CX4.
"5 how about the market size of the collapsed distribution/core,dose someone this? "
I don't know, but as specific market for collapsed distribution/core devices, that would seem a bit of "smoke and mirrors". A device such as the 4928-10G can certainly be used for other purposes then just collapsed distribution/core and other devices could be used in that role. I look more at the devices capabilities rather than how the vendor positions it for the "market".
