In the 1984 events of Terminator: Genisys when Kyle and Sarah, having destroyed the only known enemy robot in their timeline, approach their one-shot Time Displacement Engine (TDE), they get into an argument about whether they should travel to 1997 or 2017.
- At no point do they question whether they should jump forward in time at all.
- In either scenario, their goal is to travel to a point in time that is mere days ahead of Judgement Day (i.e., Skynet going online).
I suppose it would be tedious to watch them prepare over years to thwart Skynet/Genisys, the way Sarah did in the previous timeline (T1-T3). And given the poor dialog I can see why the producers would have been happy to move things along. But is there any internally consistent reason why there would be any urgency to jump forward in time to stop SkyNet?
Presumably any future enemies with access to a TDE would have already sent back as many soldiers to kill them as possible. I.e., time doesn't run concurrently. It's not like the future enemy just learned something from its T-1000 having failed and been destroyed: All it knows is that it sent one (or more) T-1000s back but that Sarah Connor and the resistance still exist in its past.
So travelling forward at the normal rate could only be a good thing:
- They could stockpile weapons, tactics, and allies (as did Sarah Connor in T2)
- They could gather intelligence
- Most importantly: They could avoid overshooting the critical point in time at which Skynet could be stopped.
Also, by not using the TDE to travel forward they could reserve a potential "do-over" to jump back in time should they fail.