In terms of the in-universe terminator timelines? Yeah, dark fate's supposed to be the direct successor to t2's timeline, and genisys is the last one, as you mentioned.
I refer to the movies by release order though, like this:
The Terminator (t1)
Terminator 2 judgment day (t2)
Terminator 3 rise of the machines (t3)
Terminator salvation (t4)
Terminator genisys (t5)
Terminator dark fate (t6)