Batman Beyond series was canceled because it struggled to sell, and now this book is re-launched as a mini, not an ongoing, with hopes that it would sell better.
Also, Urban legends 7 outsells I am Batman in Amazon.
And as mentioned here, take into consideration that issue #1 usually sells really really well, and then sales only decline from this point. Most ongoing titles don't get new readers.
If this series will sell less than Nightwing, Robin or Batgirls, Jace Fox would be in a real problem or even become a joke - the Batman of Gotham that is the least important character of the bat line.
So that's bad news, yes.
Of course, it's possible that the title is selling tons of pyshical copies because it's issue #1, but online things don't look good for Jace.