http://wiki.inkscape.org/wiki/index.php/Tracking_Dependencies indicates that 3.8 is what should be required for GTK+... This is the official place this is tracked, so if someone introduced features that are incompatible it's their problem to fix. This is no different than us being conservative about C++ features getting introduced into the codebase years after they're available in compilers... given previous practices and reasoning, this wouldn't pass the enterprise litmus test as they wouldn't update to a newer distro version a month after release. There are cases where we did decide to push past that standard, but they've been very few and far between.