As of this writing, the Intel-based Macs aren't scheduled to even appear until mid-2006, with the transition finishing in 2007. Don't fret though- you can expect any Macs you can buy today to be supported for several years after Apple stops making them.
The best answer to the question is: it depends. Do you really need a new computer now, or can you afford to wait for a year or two? Do you want to be one of the first to buy an Intel Mac, or do you want to wait until the kinks are ironed out? (If you wait until the kinks are out, you may have to wait 2-3 years before buying). Computers become obsolete quickly. Even if you do wait until the Intel Macs are out, Apple will still put out something better in 6 months anyway.
The typical forum recommendation reads as follows: Buy what you need, when you need it.
