I don't see any of the parts going the way of the dodo any time in the near (or far) future. When I say far, I'm talking bike-years, so 25 - 30 years.

26" wheels are strong and used on a crapton of big-box store and entry-priced bikes. Even if the trend to 29ers continues for the upper-price bikes, there will always be aftermarket 26ers available.
9spd isn't going anywhere for a while. Hell, if you know where to look you can still buy 6 and 7 speed equipment; and it's really not hard to find it. 9spd STI might get scarce in the future (but I doubt it). I don't see 9spd bar end or downtube going away any time soon.
Steel frames aren't going to outmode themselves for a gazillion reasons. Strong, cheap, repairable, moddable. Heavy 4130 frames like the LHT and CC are good utilitarian frames. You can beat the snot out of it and not destroy it.
Canti brakes... Ah, the divisive question: Cantis or discs? If you know how to adjust a pair of cantis, they're rim-crushingly strong. With the right pads, they're effective in almost all weather (no rim brake will work well on iced rims). They've been around forever because they're effective. The design has changed based on necessity (low-profile for clearance, development of linear pull for power,) but the basic idea is the same. Heck, there's a few new design cantis based on very old designs because of how well they work. i.e. Paul Neo-Retro, Velo-Orange Grand Cru; based on Mafac originals. Discs aren't going anywhere, but that doesn't mean to throw your cantis on the scrap heap.

I've got some friends riding long distance on very old steel frame bikes. Early 70s Alex Singer, mid 70s Schwinn, Motobecane and Peugeot, all manners of 80s frames (I have a 1988 Trek 400 lugged steel frame). Many are even riding with lots of the original equipment, with the exception of the wearable items.