HP and Lenovo already ship systems with Firefox pre-installed. I have not yet seen it defaulted to Firefox, but the time will come! after the making it (or another) default it would not be a surprise to see IE excluded.
Having said that, I just installed IE8, my first impressions are:
1. WTF! who changed my default browser without asking me? (Obviously, MS as part of the install)
2. Opens a new tab if I type in the address I want to go to, I wont use IE much, but I like to open tabs or windows when I want. I may have to look and see if/how to change the default tab operation.