According to the files published by the United States Patent and Trademark Office (USPTO), Samsung applied for ownership over the name on the 26th of June, and was granted the rights over it four days later, on the 30th. The name is specifically protected for use with smartphones, we noticed, and it's interesting that the name rights were granted with no special claims regarding font type, size, or color. That could mean that the rumor mill is right about the two devices being phablet-sized (either 5.5- or 5.7-inch, apparently), as the filing lists "S6 EDGE+" in all capital letters, while the original S6 edge has the latter part in lowercase.
You can read more about the Galaxy S6+ and S6 EDGE+ here, but here's a quick summary: the only other details we have at this point are the size of the latter (6.08 x 2.98 x 0.26in (154.45 x 75.80 x 6.85mm)), and the suggestion that at least the S6+ will sport a hexa-core Qualcomm Snapdragon 808 processor instead of a home-made Samsung Exynos chip. We've already seen the SD8080 preform with the LG G4, and have found it to be a very decent, if inferior, alternative to the Exynos 7420 inside the Galaxy S6 and S6 edge.
More as we get it!