To answer that question accurately would require inside pollster information that few have access to, but we can at least assume that the polling outfits are going to conduct more polling in the rust belt than they did in 2016. Some of 2016's inaccuracy was from a simple lack of polling in the (presumed-to-be-safe) states where the largest upsets were, and that is unlikely to be repeated this cycle. The polling error resulting from bad sampling, however, is likely to repeat - as the polls that disclose their sampling methodology show little change from 2016, and tend to oversample Democrats and generally do a poor job of distinguishing registered and likely voters.
Suppose that today's polls in the rust belt states are corrected for 2016's polling error. Currently, Trump would still lose Pennsylvania and Michigan, but would win Wisconsin. This presents an interesting possibility for an Electoral College tie, if President Trump were to also lose his single electoral vote from Maine's split vote. This scenario, however unlikely, could get extremely interesting...and messy. The issue of faithless electors (electors who do not cast their vote as the state did) would go from a historical curiosity to a profound historical event. In 2016 there were seven electors who cast their votes for someone other than the winner in their state - more than enough to throw a close, let alone tied, election into chaos. Supposing that neither candidate crossed the 270 threshold, the election would then turn to the newly elected House Of Representatives which would convene immediately and cast one vote per state, with a majority of states being required to declare a winner. The process from that point forward generally favors Republicans, but this would definitely be in the realm of the strange where anything could happen.