Underneat the seats is the carpet. The carpet is then bonded to a thick, heavy closed cell urethane foam (this is partly why the car is so quiet.) Underneath the foam is the car's floorpan sheet metal and one large diameter wiring harness.

In the long term, what you really have to be worried about is electrical corrosion. I would recommend lifting up the carpet on the passenger side and feeling around the wiring harness. The big problem areas are the parts of the carpet not covered by the closed-cell foam underneath - this area can easily admit water onto the floorpan.

If it is dry on the floorpan, then you have nothing to worry about except for a funky smell, perhaps.

Don't you think they should have come up with a convertible top that automatically closes when the car is off and it starts to rain??