"Nothing we can say" is about as positive as a statement we'll get. They continue the teases, rather than issue flat denials of "no plans at this time."
Their focus is on Wanted: Dead and they want to have a successful launch with that game.
We know that Shenmue is a more niche game, but it does have a certain amount of hype that could detract from Wanted, especially considering E3 2015 and the anime making it more of a known series.
My guess is Shenmue IV is either in pre-development or active development, but this new company seems very intent on things close to the vest.
If Sergei is a big fan of Shenmue, he is probably well aware of the problems that Shenmue III faced by having to be in the public eye so early on due to demands, etc.
Best to allow them to work on it 'til something is ready to be shown, rather than show preliminary stuff to get something out there.
If it does exist and 110 is helping out, I expect the initial announcement trailer to be far beyond anything we saw for III in the early stages.