What's to speculate? Plenty.
Are they still using PageRank or something completely different?
If they modified it, how did they do it?
Do they really use all available data? Or does the "don't be evil" mantra prevents them from using specific datasets?
What is their current "surfer model"? How random is it?
Until we have answers to these and other questions, I would say there is plenty left to speculate about.