Well...to quote Bruce Chizen (Adobe CEO in 2005), addressing Steve Jobs, when Apple announced its switch to the Intel processors (which started a huge rise in Apple's fortunes...), when he joked:
The only question I have, Steve, is what took you so long?
LOL, good one Umberto..
At some point, unless something ground breaking as far as a new sim being released, a lot more will probably convert as well. I did so in April '08 and haven't looked back. The main problem is getting those who tried FSX previously and had major issues with performance or stability, is getting them to try it again.
Even though I am building a new rig, i've been running on a 3.85 ghz C2D, 2GB of RAM, and Win XP32 all this time and flying LDS and PMDG birds with lot of AI and fairly high scenery settings and have never had any performance issues, except from those caused by rogue addons that use 32bit texture formats or were just poorly designed to begin with, and most of the time I was able to fix those addons to restore performance.
The only thing about FSX, more so than FS9, is that you need to have a good solid setup as a foundation. I was lucky to have had the late Michael Greenblatt at FS-GS do my whole setup from the ground up and I can only attribute my trouble free and good performing FSX experience to that considering my hardware is quite old by todays standards.