Personally I think Bush will win the next election and I think therefore not much will change with the exchange rate and it's likely to continue the way it has been going long term. At least until it starts to affect the US economy noticeably (if it does).
Looking back over the last 30 years the 90s have been plain sailing for the exchange rate compared to some of the things it did in the 70s and 80s. At one point for example 1 UKP would buy you $2.5.
If you plan for worst case scenarios in your business I would
consider the effect that would have on your business if it happened today and then start looking for some solutions fast!!!
Just because the $ has been stable for a decade doesn't mean it will be for the next decade!
It removes one element of risk if your processor is paying you in your home currency so doing this, if it's possible, would be a good thing irrespective of anything else.
The only problem is finding such a processor