Seeing as IE7 has only about 10% of the browser market share, I was wondering when Microsoft plans on terminating support for it. We have some browser incompatibilities to work through and we're wondering if it's worth the effort for such a small market share...
Support for internet explorer versions are tied to the support for the OS it shipped with. The most modern OS which shipped with IE7 is Windows server 2008 and support for that isn't slated to end until 2018. Ugh.
However you problem isn't really one of the end of support but rather the end of widespread adoption. That is a complex question and depends on what you define as a significant user base and what your users are like. For instance I work in an industry which is traditionally slow to adopt new technology so I still need to support IE6 and will probably have to for 4 years to come. But if only 2% of my revenue came from customers on IE6 I would likely drop support as it costs me more to support it than I am paid. Is it costing you more to support IE7 than the revenue you're getting from those users?