Over at “evolt.org”:http://www.evolt.org/ “Peter-Paul Koch”:http://www.evolt.org/user/ppk/380/index.html has an “in-depth article”:http://www.evolt.org/article/Browser_Wars_II_The_Saga_Continues/25/60181/index.html giving a good overview the current state of the browser market.
The article reiterates some points I’ve seen a few people making now, specifically with regards to the alleged state of the layout engine in IE 6:

Why is Microsoft unwilling to fix the CSS bugs that everyone’s been asking it to fix for ages? I think it’s not unwilling but unable to do so. Explorer’s code engine cannot be updated any more.

Sooner or later, browser makers run into the limitations of their programs. Their large libraries have a tendency to grow fat and hard to change, especially when they must incorporate functionalities that weren’t foreseen when the original program was written.

PPK has IE 7 being released in a couple of years at best. I think he is being optimistic. IE 7 may well arrive earlier, but the idea of MS investing in a layout engine rewrite for a product which whoever you speak to already has a minimum of 90% market share? Unless of course they port the “Tasman layout engine”:http://www.xml.com/pub/r/76 from MacIE…..but that is looking “increasing unlikely”:http://tantek.com/log/2003/06.html#endofmacie.
He also picks up on what I believe is one of the real reasons AOL picked up Netscape in the first place – namely that it didn’t want to be held to ransom by MS for use of IE in the AOL software – Netscape was used as a constant threat hovering over any negotiations between the two companies. Does anyone else find it a strange coincidence that soon after MS and AOL “sign an agreement”:http://www.wired.com/news/business/0,1367,59039,00.html that states AOL can use IE royalty free for seven years that they also quietly put the Mozilla project out to pasture? Of course, they “chuck them a bone”:http://www.mozilla.org/press/mozilla-foundation.html in the form of some continual funding in the knowledge that should they need that particular bargaining chip again they won’t have to go looking too far.
PPK dismisses Opera a little too quickly:

The future looks distinctly bleak for Opera. Nonetheless, it has time and again shown its resourcefulness and flexibility. Despite all prophecies of doom it still shows no signs of retiring from the race. It may survive, even though it has to be content with being backup Viable Alternative.

Here he completely ignores Operas increasingly good mobile browsers – perhaps the biggest growth area in terms of browser usage. If the use of mobile devices continues to take off you could well see Opera becoming a serious contender, or at least a browser worthy of consideration.