ATI Southern islands ?

Ok so we have seen how well the 460 has panned out. As an ATI fan myself i was wondering if anyone has any real idea what we should get from the SI cards that will be coming our way in the next couple of months from ATI ?
Personally I'm interested in which ever next gen, SI or 4 series card comes with a performance better than a 5770 for a sensible price.
With the prices of the ATI cards not coming down at all and the 460 prices going up i cant see those being an option so now im looking at next months 455/450 releases and am wondering if i should pounce on those or wait a month or so for SI ?

My gut is saying screw ATI they are making money out of us while the sun is shining and if i like the price point /performance of the next Nvidia cards then just make the jump. However there is a niggle that says just wait a bit and see what ATI have to offer.

I don't actually need to upgrade,it would be nice but i don't want to end up paying extra for a nvidia GPU should the SI release be disappointing.

Please try to stick to facts or calculated speculation. What i dont want is fans of either side trying to make a case for either side.

Mactronix