Well, with the release of CFMX ColdFusion will be entirely based on Java. All cfml pages will be compiled into
Servlets (just like
JSP's) and you will be able to call JSP tag libraries from cfml. I'm a CF developer foaming at the mouth for the opportunity to upgrade to MX and move my business logic out of cfml and into beans.
I'd check out Macromedia.com for some good info about CFMX... you'll probably be able to convince clients that the transition isn't really much of a transition anyway. You may even find a way to use CF for some of them without really moving away from Java. The benchmarks look like CFMX is very stable, too.