We are talking of the downside of the market, so it will still be
nVidia GF6200 Turbocache
ATI X300 Hypermemory
Why do you think Apple will not drop a dedicated graphics chip from the Mac mini motherboard, when they can have an integrated graphics core for free that does everything they want a Mac mini to do?
Obviously Apple already has a driver for the GMA 900 of the i915G chipset, so I don't think they won't be able to make one for Calistoga.
But perhaps you are right...