It's not unusual to hear all sorts of rumors about an upcoming Samsung flagship before the device is formally unveiled by the company, that's how it always is, and it's not going to change. The Wall Street Journal had reported that the S7 could feature a retina scanner, and the same rumor has now cropped up again from another source. It's not like we haven't heard this one before; even the Galaxy S5 was rumored to feature an iris scanner, but we all know it didn't and neither does the Galaxy S6.
This rumor also suggests that the Galaxy S7 is going to be more expensive as opposed to the Galaxy S6 mainly because it has the iris scanner and its predecessor does not. It's also claimed that the iris scanner will be present in all variants of the Galaxy S7 though it's unclear whether the fingerprint scanner will stick around or not, since the iris scanner will more or less do what it already does like provide easy unlocking of the device as well as authorization of mobile payments.
An iris scanner will certainly make the Galaxy S7 stand out from the competition, but be cautious, we've heard this before and it didn't turn out to be true. There's nothing to really hint right now that it's going to be true when the Galaxy S7 is formally unveiled.