How long before this computer becomes obsolete?

That will support gaming for a long time...look at it this way. Right now people run games efficiently with Core 2 Duos.... a Core i7 is an enthusiast CPU. It will be great. Maybe someday you may get another 4870 and CF them, but that setup will be fine. You can also increase the RAM as you need to.

At the least 2 years wihtout any major upgrades...
Or mayb with graphics and CPU upgrade, solid 4+ years...

Depends what performance you want out of it. The card will be "obsolete" first, then you might want some more RAM later.

Maybe two years on the CPU if you don't overclock it, 3 if you do. For the GPU maybe 1.5-2 years depending on your resolution and what games you're going to play on it, and of course if you add another 4870 down the line that would certainly help.

You should also go with a triple channel RAM kit for a little more performance.

It depends on your resolution, and triple channel does little for gaming, and most apps on Desk Top. Id guess at 16x10 resolution, 1 1/2 to 2 years with most games running full tilt, or close to it

It depends on you. My gaming computer plays rts games such as Red Alert 3 on ancient hardware at 1680 x 1050 very well. Just an ancient Athlon XP and an HD 3850.

Also depends on what you mean by "obsolete." To keep running games at full throttle, you'll have to upgrade, but that machine can continue playing games at high settings for quite some time. I had an entry level computer last 3 years before I decided it was past it's time. A high end enthusiast machine could probably stretch longer.

They are working on its replacement as we speak.

^^^^^^ True, always worth keeping in mind.

This. Gordon Moore (and others) have understood this for over 100 years.

Find the sweet spot where you get 85-90% of the performance for 50% of the cost.

Last gen stuff! Core 2 Quad is the way to go. Tons of performance, good price.

Obsolete is a silly word. There will be better parts for every aspect of your rig in a month.

How long will you get to game out of it? Well that is up to you. My brother games on an old althon x2, with a radeon 2600.. plays WOW well enough for him.. I go nuts not being able to play at max settings at 1900*1200 at all times. He upgrades every 3 years.. I tend to always be upgrading something..

That rig will last you a long time though, no doubt. How long is entirely up to you.. I bet it will still play games at medium settings for 4 years... May not be able to keep up on high settings as soon as dx11 comes out.. who knows.

My computers become obsolete when they die.

And my airplane starts to run out of fuel the minute they take off

My machines are powered on nothing but Hope alone