This is hardly surprising news, but it's news nonetheless. A new trademark was recently filed by LG for a product called the G3. This product was trademarked at the USPTO under the "mobile phones" category, so it seems quite obvious what it is for. We don't expect it to be released anytime soon, as LG's next high profile launch will be the G Pro 2.
More than likely, the G3 will come out in the summer of this year (probably in May). Current intel suggests the G3 will come with top-notch specs like a 2K display (2560 x 1440 resolution) and a 16 megapixel camera with optical image stabilization. We'll keep an eye out and let you know when more intel is released.