I also have the GP 4000s on my road bike. I've ridden in the rain a few times with them with no problems but that was during the summer months with no issues of fallen leaves and such. I do think for the winter season I may switch over to my old tires. I bought the GP 4000's for a time trial I was doing and liked them so much that I haven't taken them off since.

I saw some really good deals on e-bay for wheels when I was searching for UST's for my mtb. Maybe since you have decided to wait till spring you can keep an eye out there during the winter months and snag yourself a deal on a nice set of wheels.