Even then they probably won't switch. They'll get angry that someone stole their credit card, they'll complain to those around them, maybe back off the online banking for a while, but in time they'll forget and continue to use IE. Why? Because nobody knows what the hell Mozilla or Firefox is. Your average user is perhaps capable of separating the concepts of "computer" and "internet" but that's about as far as they tend to take it. I switched my family on to Firebird a while back and they didn't know the difference. They're still using it and they have no idea. I'll upgrade them to Firefox 1.0 when I'm back next christmas and throw on an OpenOffice 2.0 RC and they still won't know the difference. Hell, my dad is _just_ starting to explore the idea of getting a computer and doing this email thing, so I'm putting him on Linux. It handles email, web surfing, and word processing very well and you don't have to worry about worms/viruses...it's perfect for the newbie in that way.
The point I'm trying to make is that users need savvy contacts as stewards for their computers. Nobody's gonna switch to Mozilla / Firefox because of this announcement...those who are in the know have switched already, and those who aren't don't really care.