Things like product release schedules are rarely in the hands of developers. More likely, a product manager and company dictate when new versions will get pushed out.

Internet Explorer usually relies on new OS features which have to be backported. Also, Microsoft never releases IE for versions of Windows that have gone out of support (Windows XP and Vista), because they don't want to have to do the extra work to do so, and because their policy on out-of-support is exactly that: mo new updates.