Coldfire is not 68k CPU.
From freescale webpage:
With its architectural relationship to the 68K Family, customers using 68K products should consider a standard ColdFire product as their next solution. Because the ColdFire processor instruction set is a subset of the 68K Family instruction set, existing 68K customers find that designing with ColdFire microprocessors is a smooth transition.
Sounds to me like a evolution of 68k CPU :-D
And about compatibility, again from freescale webpage:
You can find tools such as an automated 68K-to-ColdFire processor converter and an emulation library available
So, i think that you only need a library for compatibility not much more different of 040 and 060 accelerators in which you need a 68040.library to work
