If I'm buying the book (basics ones), will it come with the old stats for the weapons and rules or the erata ones?

It will come with the old rules/the rules the books were originally printed with.

(in d&d, sometime the books were updated in case of major change)

I'm fairly sure the DH core book comes with the errata included, at least parts of it. I got one used and it has many of the changes listed. I don't think DW has an errated core book in print yet, but I could be wrong.

The thing is that the new weapon stats are not actually an official "errata". Instead, they are a "suggestion" for those that want less time consuming combat. This means that the old stats are still the official ones, and so all books are done with the old stats. Obviously for common weapons you can just drop in the new stats, but totally new weapons are a bit unclear, as it isn't clear whether they balance well with the new weapons or not.

Reprints of older books do not come with the errata included. The errata will be in a collected document (for DW its called the living errata). It seems that subsequent titles in the series will come with the errata for the previous books in the series. anyone can confirm that this is true?