It'll be fine for a while. If you shove one of those dedicated physics processing boards in when they become "de rigeur", It'll have very little to do, assuming developers don't make completely unrealistic jumps in AI processing complexity...
It's good enough. Of course if you don't mind overclocking then you may as well just get a 3200+ or something, as they'll probably have roughly the same clockspeed ceiling anyway.
Hell, It's a good CPU now, so why bother worrying about the future... IMO people are far too concerned about such things when buying components. All too often they make purchasing decisions based on future upgradability, only to fully replace those parts when they eventually do upgrade.
So to sum up:
Worry about "Now";
"Now", a 3500+ has a very good price/performance ratio;
"Now", the additional cost of a higher-rated CPU is not worth the benifit;
If overclocking, you may as well get a 3200+.
Oh, and try to get a Venice core if you can.
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<font color=red>"Life is <i>not</i> like a box of chocolates. It's more like a jar of jalapeńos - what you do today might burn your a<b></b>ss tommorrow."