Is $4,300 to upgrade to a 75 gallon gas water heater a fair price?

I currently live in a 3 bed 2.5 bath 3100 sq ft rancher in NJ with my wife and 1.5 year old, with another baby on the way. We have a 50 gallon electric hot water heater, which we have no issues with. We are looking to put an addition onto our house as well as finish the basement, adding 2 more full bathrooms to the mix. We believe our current 50 gallon tank will be undersized for a 4.5 bath house. We are considering 3 options: keeping as is and seeing how it works with the extra bathrooms, replacing our 50 gallon electric tank with a 75 gallon gas tank, or replacing with a gas tankless heater. We have a huge utility closet in our basement so space isn’t an issue. Our water heater will be in an unfinished utility room right next to an exterior wall, so I don’t imagine it’d be very difficult to run exhaust down the road even after the basement is finished.