Buy it and enjoy it now! The refresh could be spring/summer 2012 ... that's a long time waiting when you could be enjoying your Air now instead of speculating what SB may do better.
Who wants SB in their Air's yet anyway. If you think about it no one should. These chips are raising temps in all MBP's ... imagine how that's going to work in a thin MBA ... it's not.
SB alone does not = hotter chips. All chips depend on TDPs and you (conveniently) neglect to mention that the MBP's, both the 13" and 15/17" went UP in TDP in this refresh. The 13" jumped from 25W to 35W and the 15"/17" went from 35W to 45W. That's a big jump for no change in form factor. Those laptops run hotter 'cause their chips suck more energy.
SB has some LV chips in the i5/i7 family that run at 17W and would suck up LESS energy than the current C2D+320M combo in the Air. Hence, they'd run the same or cooler, and have better battery life.
You'll be waiting a long time then. Ivy bridge in the MacBook air Isn't coming anytime soon. Due to the fact the MacBook pro will have it first and apple will probably not see it essential to have it in the MBA for the time being until 1 or 2 years later just like c2d.
Yah, Ivy Bridge for MBP will be this time next year. LV Ivy Bridge for the MBA will be Summer 2012. That's a almost two years from the October 2010 refresh. AKA, a LONG Time for an update for Apple's new #1 selling portable machine.
Sandy Bridge is must for June on the MBA because c2d is emphatically dated tech. other competitors are ahead of the MacBook air in specs in it's class ATM and for another year if no refresh were to incur. That's why there will be an update.
While I agree with you in Theory, new data leaves me to believe it'll be October possibly before we get any sort of refresh, and even then possibly just a Spec bump to more RAM and a thunderbolt port (and hopefully BL keyboard) to Spur Holiday Sales.
And while I'd have no problems with SB in a MBA (why not want a laptop that's faster, runs cooler and has better battery life at the expense of gaming performance - who games on a MBA anyway?), new reports are suggesting the MBA is currently still selling like gangbusters.
And despite all the SB hate in these forums, I've always said it'll come down to sales numbers. If the MBA sales drop off, the refresh will happen sooner. If the sales numbers hold up, the refresh will happen later.
Current reports are saying the MBA is still selling great - in fact the Air (due to a price-drop, mostly I'd say) is selling up to 300% more than last year (when the product WAS stagnant) so I see that as meaning the refresh will not happen soon (June) and may happen in the Summer/Fall (SB or not).
SOURCE:
http://www.macnn.com/articles/11/04/04/could.reap.22.billion.per.year/
That being said, as the air now makes up for 15% of total laptop sales, and could potentially grow, I have a hard time believing that Apple would leave their hot selling portable completely stagnant for 18-20 months. That seems ludicrous to me, and something Apple's *never* done before (especially when there's a chip that would give better battery life, and save Apple $$$$$ by not having to include a separate graphics chip).