Indeed, the Kojak in size ETRTO507 disappeared from the Schwalbe website. When tihis happened for other tires, they never came back. The only counter example I know is the Kojak 32x349 folding for the Brompton that Schwalbe doesn't sell anymore but that Brompton is still selling (and there is even a special Kojak tan wall version specially made for Brompton.

If Helix ask Schwalbe, they could have the Kojak ETRTO made again but they must pay Schwalbe for that.

Now, the Kojak is a very special tire, a wide slick tire in soft rubber. It is fragile, with a limited puncture protection and the expected mileage i(n case it survives road abuse) is low. It is supposed to be a fast tire, but it isn't : almost all road tires are faster and even many tour tires are faster.
The main advantage of the Kojak is that it look great and make a bike look great.