Lexus is taking their time with filing trademarks, as the risk of losing out is not as great (RC-F almost named RC500F), as they likely own rights to LS###x nonmenclature and will file suit if necessary. They are intent on hiding many aspects of it very closely, knowing that trademarks and design patents can give away too much too early.
Is the LC coupe arriving before it? As one hears that will be debut in January 2016, at NAIAS. Nothing about the LS, unless planned for Tokyo. Lexus is already testing prototypes of both domestically, but not in the open of course. The least we've seen, is a test mule of the LS, which I just started a thread on. LC500h was also trademarked alongside LC500, which the latter is unlikely to be a 6-cylinder.
The LS500 will likely have 5.0 litre engine, like the Jaguar XJ. Whether it will be turbocharged, unlike the RC-F and GS-F is the question. This will likely be an all-new V8 I believe, not a recycling of the RC-F hopefully. The LS500h, I will not take a gander at. A non-hybrid 6-cylinder is likely a possibilty. If I like it, I might make it my first Lexus purchase when my budget allows it next year.