Hypothetical possibilities don't mean that it will ever happen.
First, a wormhole has to be proven to actually exist. A theoretical probability does not mean it actually exists, merely that it can exist. Second, space travel still needs to advance to a sufficiently advanced level to reach the wormhole. Third, the same space travel needs to be able to not only reach the wormhole, but then sustain whatever rigors may occur from passing through the wormhole. Fourth, control over the amount of time travel that occurs would likely be limited based on each wormhole, so it's possible the wormhole may only travel meaningless amounts of time forward or back, or travel so far forward or back that it imposes hazards on the craft that attempts to make use of it.
Even assuming everything is perfectly aligned and accurate time travel is possible, it's entirely possible we are wiped out as a species before we reach sufficient advancement for it to matter. Or the exact opposite of we advance so far as a species that time no longer is relevant.
Either way, it's a hypothetical question that really just boils down to two things: we have no evidence to support it ever happening up to this point, and we have no means to test any of the hypotheses which would provide such evidence as of this moment. So it's pointless, in my opinion, to dwell on the hypothetical when the practical parts of the question can still be worked on. The hypothetical only becomes relevant once we actually perform time travel, since now we have a legitimate basis to question the lack of a footprint from future time travel being visible in the present or past.
Which leads to the more theoretical answer explaining a lack of a footprint, which would be going back in time would create a branching dimension of time from the point you travel to, since your very presence there would change the course of events. Meanwhile, in the original dimension of time you originated from, it would remain unchanged since you traveled to a different time stream.
Essentially, the theory assumes time is the fourth dimension, and the fifth dimension composes of all branches of time (or multiple instances of the fourth dimension, so what pop culture would call "parallel dimensions"). By travelling back in your path of the fourth dimension, you would have to create a branch at the arrival time where your appearance changes the events of the dimension from that point forward. As such, travelling back in time would put you further back in the fourth dimension, but on a separate axis in the fifth dimension. Therefore, the original time that you originated from is undisturbed, while another instance of reality where your time travel changes the events of the future is created.
Which is all, again, theory which can't be tested yet, and is mainly supported by too few observations and some very presumptive logical reasoning.