Fivethirtyeight has Trump at 12%. Others seem to be pointing at less - I can't remember which but another poll aggregator of reasonable repute had a Trump win at 5%.Right now most of the signs are pointing to a Biden win but a 12% chance Trump pulls off another upset(assuming the stats are accurate) is 12% greater then zero(Shut up, I know 12% of 0 is 0! I'm trying to make a point).
I think it will probably tighten towards the end. Let's say a Trump win at about 20%, which is far from negligible. They key state to look out for is almost certainly Pennsylvania, because if Biden takes that he's almost certainly won, as that plus all the other states he's even further ahead in will take him over the line.