I love the Tracker and I hope it continues as a line. It currently looks like there are no trackers available. Maybe there are more on the way but it also occurs to me there might be a new version coming at some point.
Has there been any discussion about what’s next or a possible Tracker II?
I can say with confidence, there is no new tracker on the way or in development at the moment. 
They are just sold out right now.
Some resellers (depending on where you are) still have some stock it seems.
I just bought tracker mini new two weeks ago. And tried to buy tracker plus from a store but they said me that there aren’t units available until December. At the end I picked one second hand T+ in excellent condition, almost new.
so it’s being restocked?
Yes, Tracker+ is still being made, but there are some delays; no ETA for new units right now.