Here's what we're doing with our 2 year-old. He's not quite ready (maturity-wise) for a toddler bed, but he had clearly outgrown the sleepsacks. But we didn't want to use a pillow and blanket in the crib because with the side rails, there's always still a chance they would get bunched up around his face or tangle him up when he flails around at night.(Unlike a toddler bed, where the stuff would just fall over the side.) We bought a Blankeaze from One Step Ahead, which is like a sleep sack, but has legs. This way he can still walk and play around in his cib, but it covers him all night. The zipper is in the back, eliminating that pesky stripping (and then peeing!) in bed. It can go over footie PJs, or something lighter--but since the feet are open I would just use socks then.
What I like about this is that I can use the novelty of a new pillow and blanket as an added incentive for him to stay in bed when we finally do transition to a toddler or twin bed. Good luck!