Given the legal peril that Trump currently faces, there is little reason to doubt that he will call for violence (probably in his usual facially equivocal way) if he loses in November. Under other circumstances, the planning for this event with friendly state and local officeholders and militia leaders would have already begun. The polls, however, predict a Trump victory. That will have retarded any kind of planning for an insurrection.
In the short run, therefore, the state of polling at the present time is actually a good thing for the nation. If Biden wins, however, the sense of outrage will be that much more intense. A spontaneous uprising is less likely to succeed than a meticulously planned one, but it might be more violent.