Chuck Westfall said in an interview with DPReview that the new 5Ds(R) is gonna have the noise performance of the 7DII, which was kind of expected, BUT also the DR of the 5DIII... Huge bummer IMHO. https://m.youtube.com/watch?v=RSQTKM3nQ5U
I see why people get UWAs for landscapes, but for me, I've created my best landscapes with a tele or supertele. I love that compressed look and the possibility to separate a detail from the whole... I sometimes even need a 400-500mm equiv., so for me it would be the 70-300L on my 7D for portability and FL reasons, which is what I actually use. A probably better, but also more expensive option would be the 5DIII and the 100-400II and the absolute dream combo is the D810 with the 80-400.
My uncle wanted a camera for family shots and for product Images... He asked me what to buy and I recommended this very camera, the Sony a6000 with the 16-70. I had in my hands now for a day and I have to say I don't like the handling, I hate the JPEG engine and I'm not as impressed by the AF and the VF as several reviews stated I should be... Sure, RAW IQ is nice, but other than that... It is a good choice for him as a relative noob, but wouldn't be an option for me...
I do not see a 'gap' in your setup, but I would try new things in your situation.
Maybe invest in the 8-15/4L for that unique fisheye look. Maybe get the 24 TS-E for its unique capabilities. Or maybe get a MF lens, e.g. for portraits, maybe the Zeiss 135/2 or, if you have some money to spend, the Otus 85mm... Also, I find long, portable teles to be extremely important for landscapes... Think about the 100-400II.
But until then, have fun shooting with your gapless gear!
How about the Canon 35/2 IS? 600$ over at B&H, great IQ and AF, IS for handheld stuff, f/2 for more creative shots, flexible FL for both groups of two or three as well as portraits of one person... Seems to be the best option here.
Wow! Just wow!!! Only 1200$ for that kind of lens?! Matt Granger tested it out at Photokina and he was very pleased. This is going to be serious competition for the Nikon 14-24 and a no-brainer for every Canon shooter searching for a fast UWA!
The cheapest option would be the new 24-105/3.5-5.6, which seems to be quite good according to TDP. But I'd recommend you to step up your game with the Sigma 24-105/4 Art. It is in most cases sharper than the Canon version, you are extremely flexible with AF configuration (buy the USB dock for it) and it has great build quality. 70mm would be too short for me for landscapes as well as portraits, so a 24-70 would not be an option.
I would go for the 16-35/70-200 solution, because I love UWA and tele and you have got the 35-70mm "gap" covered by the 50mm. You could think about buying a 70-300L instead of the 200mm, as I often find 200mm to be too short on FF and I absolutely love my 70-300L. These three lenses would actually be my favorite travel setup.