Most toll roads in FL are now what is called ORT - open road tolling. You'll get a bill sent to you via your license plate.
Or you can stop at any gas station and buy a Sun Pass, which will get you a discount on all tolls.
Regarding I-4, yes, for the next 6 years my company will be completely reconstructing I-4 through downtown from Universal all the way to the north side of Orlando. It will not reach Disney, but if you are coming from I-95, be prepared. I'm currently helping out with that project, and was on the bid team. Go team.