This entirely depends on your definition of upgrade, and where you want to sit in the product market.
For instance, the bulk of the components of a modern consumer PC have no forwards compatibility problems. Any graphics card you purchase will use PCI-e, and motherboards will be supporting this for the foreseeable future. Additionally, optical and mass storage devices will use SATA, so you have no problems here. That rules out upgrade related issues with optical drives, hard drives and expansion cards. As an example, the DVD drive in my computer has lasted me 6 years now, and is still going strong.
Thus, all of your upgrade issues come from your motherboard/CPU. Happily, most of these can be avoided with simple forward planning. Most new motherboards support one or two SATA 6 Gbps ports, which future-proofs your SATA options. Similarly, most support DDR3 RAM, which means you should be able to use the same RAM for most of the future. The issue comes with processor sockets.
As a personal opinion, I think the upgrade cycle for CPUs is longer than for most other components. The Core 2 Q6600, which is now 4 years old, is still a perfectly solid processor for most usage applications. So long as you aren't doing something exceptionally performance intensive, you should be able to get years out of your CPU, and thus out of your motherboard.
Altogether, I wouldn't worry too much. If you assume that you need to upgrade your motherboard at the same time as your CPU, and thus view them as a single component, you can then plan ahead in that mold. I won't be replacing the Nehalem Core-i5 in my desktop machine until at least Ivy Bridge, and quite possibly a generation later. Worst case scenario, you can buy a better aftermarket cooler and overclock your CPU to get a few extra years out of it.