For sure 800 series Southbridge will be better than 700 series (that's a large part why he and I are waiting), however, I would not put it past AMD/mobo makers looking to get out first to release with 700 series Southbridge if 800 series Southbridge ends up being considerably late. Not saying that will happen, but, it could.
As for 5000 class of IGP, IMHO, they've already F'd up by calling 785G a 4200....especially when one considers that 790GX is 3300, and it's faster.
They should have called 785G something like 3250 (since 780G is 3200), and saved 4xxx for the 800 series Northbridge.
I know why they did the 4200 naming, I just don't consider what it brought to the table enough to warrant it's number, especially reaching 4xxx level....
Chuck