I should hope not. If parts on the new LHT are obsolete I hope no one sees me riding my 1984 bike!

Even if every single new MTB went to 29" rims, to many bicycles around the world run 26" wheels. I bet 26" tires will be around for a LONG time to come.

Canti-levers when set up properly work very, very well. V-brakes are easier to setup however, but require different brake levers. I wouldn't worry about pad replacements either, as again, any tech that is on that many bikes won't go away overnight.