Winter and Cyclocross tyres / tires

ok i ordered 28's. i figure 25's are too close to my 23's (which still have plenty of life left in them). all that ice and snow is scaring me.

At this point, isn't it a bit late in the game to be changing tires. I just switched out from 38 cross tires back to my 28 rear, 23 front combo. The odds of more snow are slim and on ice, bigger tires really aren't going to grip a lot more.