As 2012 is approaching we feel that something will happen with GPU crunching next year even if it starts with beta WUs.

I was wondering about the way Runtime and Points will be calculated.

For that to be coherent we have to understand how a GPU will be used. If it is one WU/GPU, with the GPU crunching in a serial way one WU after another that should be more simpler. In fact one GPU acts as a single core, very powerful but single one. A GTX580 would be one core and the GTX590 would be two core.

Runtime
There should not be much change, except that the WU would be crunched much faster in theory so shorter times per WU. But for a machine running 24 hours, that is what you can get with one core. That would be 1 day runtime/day.
In respect to Runtime a multiple core CPU with Hyperthreading is surely more interesting than a single core GPU. I get about 12 days/day when all is well with the 980X.

Points
Here it is a different matter. There should be a benchmark specific for the GPU. That bechmark will set the reference crunching performance Whetstone, Drysthone (could be over 1 TFlops for one top GPU). If we take the WCG ratio that is 1TFlops/day is equivalent to 700'000 points then from the time a WU will take to be crunched by the GPU you will get a number of points for the WU in proportion to that.
In short a GPU benchmarked at 1TFlops, if dedicated 100% for a whole day crunching WU's it would at WCG rack 700'000 points in that single day.
For points there is no discussion the GPU will be king. A GTX 580 will rack 700'000 points in a day and a 980X Overclocked can generate around 55-60'000 points at best per day. The ratio is about 11 to 1.

Today the top motherboards allow to add four GPU cards. If your power supply and cooling can withstand it, it is possible to have four dual GPU or up to eight GPU's into one big tower. That means "in theory" that such a single machine could rack a total of 4'850'000 points/day (GPU+CPU).

The future looks brilliant and full of glittering points everywhere.