There could be blood now. There was blood somewhat regularly in the Golden Era, which was also PG. Vince himself doesn't like guys bleeding. He got pissed at Bret in the 90s for blading hardcore (WM 8, the IYH with Bulldog), but claiming it was hard way. Flair got fined for it at WM8. Blood got cut way back around 1988 or so. At the start of the Rock and Wrestling stuff, blood was still very common, because it was a hold over of the old era. Once things really took off and Vince had completed his vision of what he wanted, blood was phased out and sparingly used, and when it was, it was to get over something as being particularly vicious.
PG doesn't really mean "no blood allowed". There is blood in PG movies and cartoons. It's Vince's personal preference and I don't really have much of an issue with it. I would like to see blood in cage/HIAC matches and not have matches stopped when someone gets busted open, but I really don't miss blood in wrestling. The Cena/Wyatt feud could have used blood. The HHH/Bryan beat down angle could have used Bryan bleeding.