I have been considering upgrading my 9 speed Trek DS to a Shimano SLX crank set -- but finding that 9 speed SLX crank sets are becoming hard to find. I understand that a 10 speed crank would work (or could be made to work) -- but the 9 / 27 speed system is more than adequate for my needs and I figure it is probably more reliable.

But, I fear that in 5 years or so, if the trend towards more and more gears continues I won't be able to replace worn out 9 speed components with high level parts and will either be forced to upgrade the system to 10, 11, or 12(?!?!?!) speed components or make due with lower quality components...

Should I worry about this "Planned Obsolescence"? Or should I go with the 10 speed crank and plan to slowly upgrade all the other components to 10 speed as they wear out?

I like my 9 speed drivetrain and I'd like to keep it! But it seems that the industry is pushing me ever higher if I want to stay with higher end components (SLX or better).