In my opinion Google Page Rank never dead. I think it will be updated after 2013. In previous Google updates page rank 3 to 4 times in a year. but it will be 1 or 2 times in a year.
Alexa? No! Alexa is an easy-to-manipulate ranking system that no serious webmaster can take into consideration. Personally, i had a website under50K with onl 2K UV per month just by using all thee free of charge alexa rank "hack"(if you can call it like this) tools.
I am wondering why you are so worried about pagerank, what about rankings? What about traffic? What about an ROI?