Silly question, since the Bike Industry constantly tries to make our stuff obsolete, but here goes... I'm looking at the Surly Long Haul Trucker and if I get (or build) one, I'd be keeping it for the "long haul". It's steel, it's strong, I should be able to ride it for a long time, right? But I wonder this: is there anything about the complete bike or the frame that makes it vulnerable in the reasonable future to obsolescence?

Example: my frame size comes with 26" wheels. I hear rumblings from the mountain community that 29" is the new thing. And roadies run 700c. So, would my frame end up using what's about to become "old school" wheels, and rims and tires will start fading away from the market (or good choices fade away at least)?

Another example: the brakes. The bike uses cantilevers, which folks seem to complain about in the cross world. Are discs about to take over the planet, leaving other brake systems eating their brake dust?

I don't care about new-fangled stuff, BTW, just want to make sure I don't buy the LAST of something. My bike needs to be practical.