The Year 2038 stuff is cool. Do we have projections for how much unpatched stuff might still be around in 2038 to cause issues? The benefit of getting the fixes

The Year 2038 stuff is cool. Do we have projections for how much unpatched stuff might still be around in 2038 to cause issues? The benefit of getting the fixes merged 18 years ahead of time is so those fixes proliferate, but I have to imagine there's a nonzero amount that won't/can't upgrade... Curious if there's any idea of how big an issue this could be, even if we solved everything today.