Every time this discussion comes up, people fail to see the significance of IPv4 running out. It's 2010, and folks still get confused.
The significance is this: There are massive growth regions in the world that will only be able to purchase IPv6 addresses within the next year or two. And if you aren't playing the IPv6 game, then you're shutting you and your customers off from all those various markets that will open up in years to come.
There's only so much can be squeezed out of IPv4. But regardless of how much can be squeezed out of the existing space, the regional registries are likely to run out of /24's they can allocate within a year. See for a guesstimate: http://www.potaroo.net/tools/ipv4/index.html That is, in 2012, much expansion in growth regions WILL be IPv6 only.
You're shooting yourself in the foot if you refuse to bring yourself up to date.