10 years is a long time for network electronics to be usefull, in 1995 I was using 10 meg shared hubs in the closet and 100 meg shared FDDI at the core. But my wiring (both fiber and copper) from 1992 still works.
Thinking 10 years in a building, I would be thinking 50 nm multimode fiber in the core and cat 6 copper to the desk to last 10 years. You may see a need for 9 nm single mode fiber at 10 gig and up. (how far is ten floors? 50 nm multimode will go 500 m at 1 gig, 300 m at 10 gig)
5 years is a better guess for the electronics. Then the core may move out to the edge.
Today I would plan on a gig core, servers, and power users and 100 meg to the average desk (all switched, all managed, all QOS) with plans to go to 10 gig core and 1 gig to the desk within 5 years. (I would be getting gig NICs now)
Be looking at VoIP for a new install. (I wonder if he was asking about the data or the phones?)
I tried to remain child-like, all I acheived was childish.