As far as "Will the general public recognize it as a kilt without one?" question...
Yes. The general public has no problem recognizing kilts. For example, my first few kilts were Utilikilts (which don't really go with a sporran) and the general public seems to have no problem figuring out that it's a kilt; and as contemporary kilts they are the most likely to be mistaken as skirts.

Personally, I don't think you need a sporran. Yes, you need something to carry your stuff. That's why I like the idea of contemporary kilts; they're easy and come with pockets.