The good news is that both Camino and Safari are better browsers, building on the standards support that was introduced with the Mac version of IE. The bad news is that designers and developers will be building sites for the current crop of Internet Explorer browsers for quite some time. Longhorn (the next version of Windows) isn't scheduled to appear until 2005, and will most likely be the next time that Microsoft updates their browser. Even then, most will not upgrade right away, and 90% of users out there will still be browsing with versions 5 and 6 of IE.
I suppose it could be worse... CSS support for browser versions 5 and 6, while still buggy in spots, is manageable, and real-world usage of CSS-based layouts is well underway.