I'm figuring that altimeters will be going the way of VORs, soon enough. GPS can locate itself in three dimensions (that includes altitude) and doesn't care what weather system is passing through. I don't think affordable, high-altitude "radio-altimeters" (use a reflected radio signal to measure distance to the ground) are a thing we're likely to see.
i think your right about that. i was at a eaa chapter meeting last month. one of the guys from garmin came and did a presentation on the 430 and 530. if i remember right he said that gps is already more accurate means of finding your altitude. i believe he said they usaully say it will be accurate to +-1 foot. it is good enough to do gps only appoarches (don't let the faa know if you do one). ils may be a thing of the past in the next 10-15years as well. btw when are the vors going out? last i heard was in 2008.
