I'm not sure how anyone knows whether jail time is likely. What I've read, and what Cy Vance said on Meet the Press, is that this has actually never been prosecuted as a felony. Falsification of business records is always a misdemeanor because the statute which says it can be a felony is unclear. Basically, for it to be a felony, Trump has to have falsified the records in furtherance of another crime. Which here is difficult to prove.
They are anticipating this as Trump's number 1 defense, that it can't be prosecuted as a felony because there is no proof of intent to commit another crime. If Trump succeeds in this defense, then it's a misdemeanor, and since the misdemeanor has a 2 year statute of limitations, Trump gets off scott free.
But if Bragg succeeds in proving intent to commit another crime, and it's a felony, then there is no precedant to determine how much, if any, jail time is likely.