The biggest competitors to Office 2007 are really earlier versions of Office. The changes to the GUI combined with the lack of real user demand for change means that upgrades are slow in rolling out, but there is now a gentle drift.
As large corporates now go for standardized builds of Windows rolled out to thousands of users at a time, a few users who like the multi-threading capabilities of Excel 12, or the really cool components in the new Word, may simply be ignored.
Microsoft makes real money out of its users when they upgrade, not while they use the product, so anything that slows this process is not popular at all.
That means, that if Microsoft were to lose the plot and kill VBA, a huge wave of powerful users would flatly refuse to allow upgrades. As with credit derivatives, a large percentage of all the money made (or lost) by banks goes through VBA, aided and abetted by C++ XLLs.
The final reason VBA isn't going away comes from the irony of the Windows monoculture of many firms, that - because everyone has to use the same collection of software, configured much the same way - the corporate configuration has to be capable of running less mainstream applications that are important somewhere in the firm.
So, although most users of Office do not code VBA, and a large percentage don't even use VBA code written for them, enough use is made somewhere that they must have the facility. Think of VBA as like the ladies toilets in a firm where 99% of the staff is male.
A version of Office without VBA would therefore find it extremely hard to penetrate corporates and even quite a few smaller outfits, because it would find it difficult to co-exist with previous editions.
VBA will, I believe, be with us for a long time. You might not like it, very few people do, but the reality is VBA will be providing work for a lot of people in IT long after Windows Vista is a memory.®