Like many places, we had a warm winter last year. Yay. But it can get chilly, even cold.
I come from a place where 0 degrees is part of winter. People complain about it, but nobody is surprised or shocked when it drops from 12 to 0. And they delight on the rare occasion there is a heat wave and it goes up to 38 or 45. Forty degrees - Woo Hoo. It's why I moved to Florida, lol.
So, when I say it can get cold, I'm not talking 58 or 60, like many people would define it. It can honestly get cold. On rare occasions, it will dip to freezing overnight. But freezing is about as low as we go, ever. We do not get the bitter, "suck the breath out of you" cold that some places have. If it dropped to zero in Orlando, they'd talk about it for fifty years. If it gets low enough to turn on the heat, it becomes a topic of conversation.
And even if it is cold in the morning or evening/night, it can still be quite warm at two in the afternoon.
Pack for warm. Pack a little for cold. If you wear warm clothes down and pack one other warm outfit, you will likely be well prepared. Even if it is uncharacteristically cold, you would still have enough to get you through, with a little laundry.
And if you're willing to shell out for a sweatshirt, you're good to go. Disney sells a lot of crappy clothes, but if you're willing to pay Disney prices, you can still get sweatshirts that will last for years and years, making them a bargain, long-term. At least last year, they were still selling good some quality sweatshirts.