No, you are not limiting yourself to not using Railo in the future. I have come across very very few incompatibilities - one trivial one I can think of - with ColdFusion in Railo's CFScript implementation.
Railo on the whole strive for cross-compatibility with ColdFusion with their CFML, and they generally only veer away (by design) when the ColdFusion way is just wrong in any sensible way of measuring such things. But even then, generally Railo has a "warts and all" approach.
As there's not really much to CFScript, and the functionality of control structures is fairly "pre-determined" (eg: there's only really one interpretation of how an include
statement can work), I don't see this becoming a problem.