Fujifilm X-T3 will be officially announced around Photokina 2018 in September. According to rumors, X-T3 will have a brand new image sensor. The sensor on X-T3 will be 26MP (stacked).
According to recently article from Nikkei, both Canon & Nikon is set to release their first full frame mirrorless cameras around Photokina 2018 in September, and release date is in 2019.
After Sony has announced the new a7 III (Adorama/B&H/Amazon) full frame mirrorless camera, now next full frame mirrorless camera from Sony should be Sony a7S III, to replace current a7S II (a7S II was announced on September 11, 2015). According to Sony Rumors, Sony a7S III is rumored to be announced in the second half of 2018, around Photokina in September. Though NAB Show is in April, 2018, there is no rumors on a7S III to be announced in April.
After Sony announced high-end Alpha a9 full frame mirrorless camera, there are more and more talk on Canon’s full frame mirrorless camera. According to latest rumors on CR, the first Canon full frame mirrorless camera is scheduled to be announced around Photokina 2018 in September. And after that, there will be more Canon FF mirrorless cameras to come. According to CR, Canon full frame mirrorless will use EF mount lenses as their native lenses.