Honestly, the potential that Windows 7 will not suck will be a bigger threat to Apple than the global recession.
What tends to get lost in the hysteria of recession coverage is that the upper, upper middle, and those solidly middle class people who still have jobs all still have money they can afford to spend to a certain extent. Sure they might not be maxing out the options on things they buy, but if they could afford Mac prices before the recession they can still afford Macs now, it just may be a 20-inch iMac instead of the 24 incher, the 2.0 MB instead of the 2.4, etc.
The real problem for Apple will be the possibility that a successful Windows 7 roll out could wipe out customer negativity that came with the Vista rollout. A Windows that sucks considerably less be just enough to stop the growth that Apple has enjoyed the past couple of years.