what is user changeable?

Processors in Apple portables are not changeable. RAM and hard drive are the only components that can be changed by the end user.

 

You obviously don't know a ton about computer hardware. So why are you concerned about upgrading from Sandy Bridge to Ivy Bridge, when you don't even know what the benefits are?

You're basically saying this: You don't want to buy a new computer because a better one will be released later.

What you need to fully grasp first is what Sandy Bridge has to offer, and what it can do in terms of raw and real-world performance numbers. Ivy Bridge isn't going to be a significantly giant leap forward. With Sandy Bridge comes Ivy Bridge, and with Ivy Bridge will come another processor line... and all of this comes out at a relatively consistent pace.

Anyways, the direct answer to your question: No, you cannot upgrade from Sandy Bridge to Ivy Bridge on the same computer. You can obviously, however, sell an old computer and put that money toward a newer purchase. Sandy Bridge is a different socket than Ivy Bridge, so an Ivy Bridge processor will not physically fit in a Sandy Bridge processor socket; that's the first and most obvious problem with upgrading. There are many more technical aspects which would prevent you from upgrading the processor in a Macbook Air.

 

If you wanna change the CPU, you have to change the whole main board and it has to be from the same model/same year(i.e. i have a 2.4ghz 13" 2010 MBP, I could change the main board to a 2.66ghz from the same model but the cost is of a refurb MBP already).

 

Highly unlikely(Read as - Never in No Way, By No Means). But i wish it could too!

Actually there are computer chop shops (i know of at least 1 in sunny singapore) that would allow you to swap some of the soldered on parts for upgraded components. For example i can have the cpu in my 2010 base 13" macbook air which featured a 1.86 ghz core2duo swapped out for a 2.13 ghz core2duo, i can also have the ram upgraded from 2gb to 4gb although 8gb is out of the question as they would need to rewrite the bios. It would void the apple warranty and would be quite costly. The ram "upgrade" from 2gb to 4gb alone would have cost me $300. Also for the processor it is subjected to availability of parts.

Now this is for something within the same architectural confines. What you are proposing is swapping between 2 different architects altogether and so there really is no way to upgrade from one to the other.

Hope that helps. If not it was fun typing anyway!