Spin will always be neccessary, and hopefully therefore produced in quality, at more grounds than not in India and Sri Lanka. Already mentioned by ss is Mumbai, Chennai is another that comes immediately to mind, and I'm sure there are many other grounds around India that routinely produce turning surfaces. I'm also fairly confident turners could be produced to order at grounds which tend to produce flatter surfaces too.
However, quality spinners have always been rare in Australia; not for a long time has fingerspin been a viable option (Mallett's the only decent fingerspinner since covered wickets, and even he was only successful for 20-odd Tests), and wristspin is an incredibly difficult thing to bowl to the requistite standards of accuracy, and to expect someone else immediately after a Warne would be expecting a fair bit (not impossible Rob, but expecting a fair bit).
Equally, there's never been a quality wristspinner in England's history, SF Barnes aside, and he was a freak. Fingerspin used to be a highly viable option over here in the days of uncovered wickets, but hasn't been since they were covered, because most of the grounds in this country (including all the Test ones) don't tend to produce turning surfaces. Fingerspin is rarely a viable option over here.
South Africa and New Zealand, meanwhile, have never produced any wristspinners of real note since the 1910s, and even only the odd particularly good fingerspinner (Tayfield, Vettori).
So spin should not be a worldwide phenomena for a fair while, at least not to offer any threat. It hasn't been since the 1960s and it's really remarkable that in the 1990s and most of the 2000s there were two wristspinners of the highest quality and one other who improved greatly as the latter decade wore on (Kumble). That sort of thing is going to be rare, and we've sort of grown used to it, and it's probably going to take a fair few years to re-adjust expectations, and realise spin of the highest quality is actually an exception, not a rule.
