I'm not so sure. If half of the value of the app you are developing is that it will still work 5 years after your consulting gig with no intervention, then it's hard to fault someone for choosing IE.
Maybe you've had different experiences, but I've had very few problems with forward compatibility in all of the major browsers (IE/FF/Chrome), and I don't know why that would change going forward. Actually, I'd go so far as to say that if you develop your apps to work cross-browser, they're more likely to work in future versions of IE than if you specifically target your dev at a single version of IE. Also, just because I do 90% of my dev work where there are good tools, doesn't mean that I can't or don't test in IE 8- (depending on the target audience).
Having something that will work 5 years after your consulting gig is not a problem - avoid browser specific features and try to stick to the HTML spec as close as you can.
With chrome (and now firefox?) you kind of are obliged to update... Right? Due to their update scheme I've at least gotten the impression that they won't fix security issues in older versions, but I could be wrong.
Firefox has a little middle ground where you can use specific versions outside of the fast release cycle and still get security updates. At least that's the plan. https://wiki.mozilla.org/Enterprise/Firefox/ExtendedSupport:... You don't get the 10 years of support that MSFT might provide for (some) versions of IE, but it's not like you have to upgrade every 6 weeks either. Also, because Firefox is open source, they're hoping that someone else will pick up the slack and continue to support older versions.
I haven't heard of any similar program from Chrome.
