Some clarity follows from the placement of reasonable limits on the various rates of obsolescence effecting each of a bicycle's bits. Frames are for keeps, or should be, I think. The life of wheels varies. Group sets: 5 to 10 years. Cables and chains: 2 years on average. Tires: a month to a year, depending on use and whether they're soft or hard, ie, for racing or training.
For the doped up A-grade club racer on a special diet and training regime, an entire 10K+ bike may be deemed obsolescent after just a few seasons. For this rider it's full carbon frames, zipp wheels, groupsets as seen in le Tour, latex tubes, hopes dashed and good riddance.
But for newcomers willing to learn from old hands, the obsolescence dilemma can be approached in a more thoughtful manner. The astute rookie might notice in their club at least one owner of a 1980s Colnago, for instance, with the original saddle, stem and Cinelli criterion bars. Of course the bike will have seen a few sets of pedals and wheels, even more groupsets, and dozens of tires. But that is not to say it is grandfather's axe. No, it is still someone's Colnago, still bringing him pride, and the occasional victory in C-grade. This guy, let us remember, is now in his 50s, and each time he polishes his old bike for race day, he is connecting with his own glory days, when this bike that set him back in his quest for home ownership was part of a greater quest to be the next Indurain.
Returning to our cycling newcomer though: among the prospective role models the newcomer might look to, would any be still riding softrides, or slingshots they bought in the eighties? Come to think of it, would any softrides or slingshots even have outlasted their first set of tires? Neither of these avant-garde masterpieces would now fetch more than a few bucks on ebay. The argument I am constructing, is that the carcass (frame, fork, build kit and saddle) of a competition bike will be held onto and treasured if it is slightly rear-garde, not avant-garde, in its design, and if its branding lends it prestige. If today you bought a more conservative bike of the kind I'm describing, in ten years time you will gladly shell out for the latest new wheels, and once every 6 or 7 years you will flip on a new groupset, if you happen to see a good set selling for cheap with a last-season run-out.
I once read a fascinating book called Analytical Philosophy of History, the thesis of which casts serious doubt over this crazy notion of future-proofing. The most we can say about the future, is that fragments of stories we now tell of the past, will make their way into stories that will be told of the past, in the future. (Maybe read that last sentence twice). Otherwise, everything is up for grabs. Whole bikes might be grown from intelligent algae, for all we know. But if that were to happen, I would hazard to guess some algae bikes will be fitted with Brooks leather saddles. Future histories of cycling, will take account of Brooks saddles, along with an unknown array of such deeply ingrained traditions. Head badges: I can't see algae bikes not having head badges.
Traditions are waves with almost guaranteed momentum, that, even if you are buying something so of-the-moment as a performance racing bike, can be trusted to carry you into the future. By contrast, novel technology has a poor reputation. We only remember those breakthroughs that stuck—STI levers, derailleurs—but even then, cyclists' first love, essentialism, will cause anti-tech reactions such as the fixie craze we have just witnessed, or mountain bikers going back to V-brakes or mustachio handlebars. If we weren't more in awe of elegance, than we are in awe of technology for the sake of technology, then we would add motors, now wouldn't we! But cyclists always want less, not more, in a bike.
In conclusion, and in anticipation of an entry to come, I would like to say how much simpler bike buying becomes when pure speed isn't the aim. Tradition becomes the central concern. Which reminds me: I must buy that Raleigh back off of Hamish!