It seems so. There haven't been any new releases for a while, suggesting that they've been discontinued. Maybe it was due to various reasons like low sales or changes in the publisher's strategy.
It's hard to say for sure. Sometimes, factors like low popularity, changing market trends, or issues with the publishing contract could lead to a manga's discontinuation. For Slam Dunk, it might have been a combination of these.
One example could be 'The Witcher' series in some of its early RPG forms that had elements which were later discontinued or modified. Another might be some older 'Final Fantasy' spin - offs that had RPG elements for adults which are no longer in production.