I'll be there most of next week (well, actually 60 miles away from WDW, you might say I am already here) and the latest forecasts are predicing highs of around 72 and lows in the low to mid 50's. Note that the low temp usually occurs just before sunrise so, while it will cool down as the sun sets at night, it will probably remain in the 60's while the parks are still open. How hard the wind is blowing will make a big difference as to how it will feel.
For me, visiting the parks to do all but the water rides when the temps are around 70 is idea. It is cool enough so that you won't get all sweaty, but warm enough so that you can get by (during the day anyway) with shorts and a light shirt. A light jacket for the evening hours would probably be needed, but I see no need to bring the winter coats.
I plan on taking jeans, shorts, short sleeved shirt/tee shirts and a jacket. I will do the shorts and light shirt in the day and switch to jeans and jacket in the evening.