The pricing formula for manuals and related issues (.pdf et al.) have been
discussed at length on the list but one thing is clear, the sale of manuals
accounts for a significant portion of StataCorp's revenue.  It is no doubt
their secondary line of business. Changing the pricing strategy, or
introducing .pdf's (I hope I won't be starting a new thread on this) would
correspond to a significant change in business model.
I would think much of this would depend on whether Stata has some big 
backlog of V. 7 manuals.  If so, it could do like bookstores do and sell 
them at clearance prices or even just give them away to academic programs 
in developing countries or to libraries.  Barring such a backlog, I doubt 
they'd want to print additional V. 7 manuals.