Though in principle I agree with the previous post, one could argue that Polonius would have been surprised.
So much of his policy towards Ophelia, in instructing her to no longer see Hamlet or give any of herself to him, was based on the fact that he thought his love for her was false and that he was out of her league really. He goes on and on about how it is just a trap "springes to catch woodcocks" or just a flame of youth that will be extinguished once Hamlet comes to his senses as the heir to the throne.
Even Laertes thinks that Hamlet's affection is false and counsels Ophelia to be careful.
So if you believe that Polonius honestly thought Hamlet was out of her league, he likely would have been pleasantly surprised by the idea of Hamlet actually marrying her with the Queen's consent, particularly since it would have more fully vested him in the royalty. As his goal seems to be to be the best "yes man" ever, this would be a lovely surprise for him.
In Hamlet Act V, scene i, Gertrude's eulogy is brief:
Polonius, if he had been alive, would have agreed with anything the King or Queen said. He would have liked the word the Queen called Ophelia, a "maid" (a virgin), though he knew she might not have been. (Branagh's film version shows that she wasn't.) Polonius was paranoid the entire first act that Hamlet had seduced her. So was her brother, and he jumps into her grave out of overprotectiveness bordering on incestuous jealousy.
Polonius was a fawning fool. Gertrude might have said that she hoped Ophelia would have been the gravedigger's bride, and he might have agreed. Alas, I exaggerate...
Not only would Polonius agreed with the marriage, he would have echoed her speech with a long-winded one of his own. Two hundred words on flowers, death, and marriage. All of it nonsense. Remember what Gertrude told him earlier: "More matter and less art."
Polonius was a windbag and a hypocrite. He used his daughter as a pawn for his own spiteful fetishes and for the King and Queen's vicarious meddling into Hamlet's state-of-mind.
After Ophelia goes mad and the inner-turmoil begins, Gertrude is saddened by what has happened to Ophelia. Ophelia loved and respected her father, Polonius. Polonius was a good father to her but asked her not to trust or to be involved with Prince Hamlet. Ophelia was upset at first because it was obvious how much she loved Prince Hamlet. Polonius felt that Prince Hamlet couldn't be trusted and forbid Ophelia to see or speak to Prince Hamlet. Ophelia is hurt by this decision, and decides to obey her father's wishes. Ophelia is also asked by Laertes to stay away from Prince Hamlet. Opelia loves and respects her father and brother, so she decides to obey both of their requests.
At the same time, Prince Hamlet learns that his uncle Claudius has killed his father. He sees his father's ghost appear and wants revenge. Prince Hamlet begins to feel uneasy about the Kingdom of Denmark and about everyone in the kingdom. He begins to act differently and begins to figure out what revenge will be had on the new King Claudius. Prince Hamlet goes to attempt to confide in Ophelia but he senses somethign isn't right with her. Prince Hamlete doesn't know that Ophelia is forbidden to speak to him and she's not acting herself either. Prince Hamlet senses this and also senses that they are not alone and treats her disrepsectful and not with love. Polonius sees this and goes to King Claudius and Queen Gertrude with his observations. The King and Queen are surprised but notice he has been acting strange. Queen Gertrude says that his strangeness is because of the death of his father (her deceased husband) and because of her re-marriage in a quick time to King Claudius (Prince Hamlet's uncle) and that all of these changes are causing him to be in grief. Polonius disagrees and asks for them to take a second look.
The King, Queen, and Polonius decide to have Ophelia meet with Prince Hamlet. They will be spying on their conservationa and meeting to see if Prince Hamlet has gone mad like Polonius accusses him of. They will be watching Prince Hamlet's moves and actions. Little do they know that Prince Hamlet is watching everyone else's moves and actions because he doesn't know who he can trust anymore.
Prince Hamlet and Ophelia run into each other and Ophelia is kind and warm to him. Prince Hamlet senses that they are not alone and that she is lying so acts out on her. Prince Hamlet yells and curses at her leaving her shocked. King Claudius and Queen Gertrude see this and believe that Prince Hamlet indeed has gone mad and that Polonius is right.
Ophelia is upset that Prince Hamlet spoke to her like this and Prince Hamlet was proving his point to the rest. Prince Hamlet is in love with Ophelia but he never gets a chance to tell her until he sees her funeral.
Queen Gertrude saw herself in young Ophelia and wanted her to be Queen oneday. Queen Gertrude wanted Ophelia and Prince Hamlet to share the love of oneanother and Denmark.
Polonius would be surprised to know that Queen Gertrude went along with spying on Prince Hamlet and putting Ophelia in a difficult situation. Queen Gertrude should have stuck up for her son and for Ophelia because she knew their love was real, instead she was misguided and lead by her new and evil husband, King Claudius.