No NEC requirement. Obviously, you will need one or the other depending on which type is installed, but no requirement to have both "just in case." I will use the existing 240V circuit whenever an electric to gas conversion is done.
All of the clothes dryer manufacturers that I can think of, whether gas or electric, require venting to the outside of the home. I would have to research to find a building code covering these. Menards in Illinois had an electric model made by Haier 15 years ago that might not have required outside venting, but it was something of a European model that both washed and dried the clothes in the same compartment. It really didn't dry much.
None of the manufacturers of residential gas ovens and ranges require outside venting that I know of. According to ANSI Z21, unvented appliances (ovens) are allowed to produce a maximum of 800 ppm CO "Air Free". Dryers usually produce very little CO. I have tested several gas dryers that produced 0 ppm CO. However, the potential for poisonous levels of CO from stoves and ovens is very real. It would be best for safety and comfort to have an exhaust system for these appliances.