There is a rhyme and a reason to product launches, and I am sure there are multiple marketing studies done by Samsung, the carriers, etc, as to release dates but rarely does anything release on a Saturday. If Samsung is going for the 10th in most of Europe, as it seems, I doubt they would push it back by a day in the US. The carriers would also have to foot the bill for Saturday delivery and there are some places were FedEx or UPS or the USPS don't do Saturday delivery. So unless Samsung is willing to let the carriers ship it early, in which case why not just let everyone have it on the 10th, a Saturday launch has more negatives then positives. They will sell the same about of S6's, if not more, by launching on Friday in any event.
Regardless, it's just a day difference. Friday or Saturday, I'll just be happy to get one.