Intel Mac, when it'll the old ones?

In my office there's an non-intel Mac running years, and I'm considering ask my boss transfer to Intel Mac.

However is it working well? Seems Intel Macs doesn't run classic Mac applications I bought before.

I don't know when will Intel core replace the whole old ones, maybe take a long time, or even worth t?

(Have no plan making Mac apps ATM)

Apple is known for discontinuing backward support. My company services Putnam / Penguin Publishing Servers and systems in the US. One of their offices in California has a G4 server and a library. The server is less than 4 years old and it is already difficult to get parts for...

I remember every three to four years Mac would come out with a new printer and kill one of the old models support.

Well it is a smaller company.

Intel Mac support will only have limited legacy support. I am not one of their programmers but as I understand it this has to do with modifications to the BSD core engine that they are currently using as their OS. This is only rumor among the Apple Techs in the office... does anyone know more?