It is hardly a pipedream if Havok FX is going to have it anyway plus
Novadex has indicated doing it plus ATI just came out with a press
release supporting it.
The real issue is about scaling. People probably remember having to
manually configure settings to get a game running on their system
limitations. It has been gradual, but game developers are now usually
including game scaling utilities, some better than others. They are all
now usually including some kind of automated or semi-automated scaling
in their Options to determine what your system can handle. The latest
rather amusing example is Steam evaluating whether your system is up to
snuff or not.
The main factor with GPU based physics acceleration is that a
developer can almost depend on a PC to have a graphics card, but it can
be real hit-or-miss whether it might have a separate physics
accelerator card. So, in conjunction with scaling and graphics card
physics acceleration, tests can be done to see if the combination will
work for a particular system and it is up to the individual whether
they use it or not.
As for the loading and number of GPU's, there are already several
dual-GPU cards out with more on the way, a lot less power than two
separate cards. But there was even an article a couple days ago about
dual dual-GPU card systems, yes, a quad SLI. Expensive as hell? Yes,
but then everything starts out that way.

  GPGPU physics makes no sense, just from an efficiency and cost
staindpoint.  Buying a second graphics card jus to run physics, at 300-400
dollars, drawing about 40-80 watts of power,  vs. 200 dollar physics card
drawing 25 watts of power.  Until GPU's are ridiculously overpowered, this
stuff is just going to be a pipedream.

Thanks. I'll replicate it here again....

I have not read the Havok article yet. However, it would be very nice
indeed if it can be tailored for SLI configurations and the USER is
allowed to trade-off resolution/AA vs physics to maximize the
frame-rate. Not all of us require 2048x1536 @ 8x AA photo-perfect
pictures when we play our action games. Seems as if the full x8 or x16

PCIe bandwidth will certainly get used.

John Lewis
- Technology early-birds are flying guinea-pigs.

Thing they don't say about this all singing all dancing physics on GPU, is
what affect its gonna have visually, i.e. is it going to force us to drop
resolution, FSAA, AF etc. The GPU cannot render everything and do physics at
the same time without any detrimental affect on frame rate and or visual
quality. I can accept arguments from others re multi core CPUs rendering the
physics on a 2nd or higher core, but one GPU? I can't see it.

Or are we all going to have to buy stuff like the  Asus Extreme N7800 GT so
we don't suffer too much a performance hit?

I think Mr Lewis' sig is appropriate.

http://www.havok.com/%20index.php?option=com_content&task=view&id=187&Itemid=77

Havok FX supports GPU-accelerated physics

Havok announces plans to support GPU-accelerated physics through Havok
FX™.  This new product from Havok will utilize the native power of
Shader Model 3 class graphics cards to deliver physics effects that
integrate seamlessly with Havok's industry-leading game-play physics
technology found in Havok Complete™.  Havok FX will be cross-platform
and will take advantage of current and next-generation GPU technology
to deliver eye-popping effects that visually enhance the gaming
experience.