The rumor from Nokishita (a Japanese photography equipment blog) is that Sigma is going to release five new lenses before Photokina.
Now considering that Sigma produces its lenses internally at its factory in Aizu and manufacturers most of the parts for those lenses internally as well… I’m kind of guessing this is a ‘leak’ from Sigma’s marketing department rather than a loose lipped supplier. So good chance all five lenses are very real and will be released promptly…
Sports!
There will be two Sport series lenses, a 70-200mm f/2.8 Sport lens, and a 60-600mm f/4.5-6.3 Sport lens. I’m betting that these lenses will only initially be available for Canon and Nikon mounts.
While it was rumored that the 70-200mm lens from Sigma would be a Sport series lens… I am still betting that they have a 70-200mm Art series in the works and a 70-200mm f/4 Contemporary lens as well. It genuinely makes zero sense for Sigma to not manufacture such high volume and profitable lenses. They’ve got to be coming at some point.
The Sigma 70-200mm f/2.8 Sport series lens 
The Sigma 70-200mm f/2.8 Sport series lens
The Sigma 70-200mm f/2.8 Sport series lens
The 60-600mm is seemingly meant to directly replace the now discontinued 50-500mm Sigma zoom lens (you can still purchase for various mounts but once they run out that’s apparently it).
The Sigma 60-600mm f/4.5-6.3 Sport series lens 
The Sigma 60-600mm f/4.5-6.3 Sport series lens
The Sigma 60-600mm f/4.5-6.3 Sport series lens
Firm specifications for these lenses are not known but expect both to be quite heavy. The Sport series is not about weight reduction (that’s what the Contemporary series is for) and both lenses predecessors weighed quite a bit. Enough that weight was always the complaint from consumers at least.
Art!
There are also two new Art series lenses going to be announced… a 28mm f/1.4 and a 40mm f/1.4. So even more f/1.4s are being added to Sigma’s pretty impressive lineup. I’m betting that these lenses also will only initially be available for Canon and Nikon mounts with E mount versions coming out months later.
The Sigma 28mm Art series lens 
The Sigma 28mm Art series lens
The Sigma 28mm Art series lens
I’m not sure who exactly is going to like the 28mm f/1.4 best… astro-photographers or landscape photographers… or maybe urban photographers? But I’m sure it’ll be quite good. All of Sigma’s most recent wide angle lenses have been stunningly good and have received enormously positive reviews.
The lens that has me the most intrigued is the Sigma 40mm f/1.4 Art lens… it’s an unusual focal length and yet every 40mm lens I’ve heard of or used has ended up being really interesting and useful. I’m hoping that the 40mm gets priced relatively cheaply because I really want to try it… but at f/1.4 that’s not exactly likely is it.
Contemporary!
The last lens Sigma is planning to announce is a 56mm f/1.4 Contemporary series lens… this lens seems to be meant only for mirrorless cameras and possibly ASP-C only. With a crop factor of 1.5x a 56mm lens would give nearly the same angle of view as an 85mm full frame lens. This may be a Sony E mount only lens.
Which would make sense… an f/1.4 85mm portrait lens would sell quite well against Sony’s overly expensive 85mm lenses. Sigma’s will probably be cheaper, smaller, and probably have better optics to boot…
The Sigma 56mm f/1.4 Contemporary lens 
The Sigma 56mm f/1.4 Contemporary lens
The Sigma 56mm f/1.4 Contemporary lens
Ultimately…
I’m glad Sigma is keeping up the pace for developing new and useful lenses. We live in an absurd world where Canon and Nikon can’t seem to make anything genuinely new or competitive and Sony can’t make a single value lens.
More options, and from a daring and caring company, are definitely welcome.