Not just for license-dodgers
Trying to dodge paying for a new license going SPARC->x86 isn't really the issue -- I doubt this software is exactly cheap -- rather it's that many sites are running software that is no longer supported, either the vendor has kicked the bucket or they've simply decided it's too much like hard work to keep supporting it.
And in any event if you're buying smaller machines Sun is about to screw you over by dropping all the low-end UltraSPARC gear. All you'll have left is Niagra, and while I'm sure that's very nice for web servers it's not so hot for big chunky batch processing jobs. Being able to take your existing binaries and have them "just work" on something like an X4100 is a nice option to have.
Not that I'll believe this really works until I've seen it for myself, which may never happen as we're freeing ourselves from dependence on SPARC and moving as much as we can to Solaris on x64.