The short answer
It is a serious scholarly position, but the evidence of his working life points the other way. The Prince reads like what it seems to be: a man writing up a fourteen-year file, for the family who could give him a job.
The case for satire
In 1958 the historian Garrett Mattingly argued that a committed republican could not have meant a handbook for princes, and that it must be satire. Others have read it as a trap set for the Medici. Both readings are in print and worth reading.
The case against
Set the book beside the dispatches he wrote on the day and the same men, towns and judgements turn up, sometimes word for word. A verb he used in a letter of 1498 reappears in chapter 18 of The Prince fifteen years later. What he said of Borgia's fortune from Borgia's court in 1502 opens the book's account of him. Satire does not usually come with its author's working papers attached.
And in the letter where he first mentions the book, in December 1513, he weighs whether to present it to Giuliano de' Medici at all, and says necessity is pressing him.