I wouldn't think so. The only slot that would likely be affected would be the 4th for the G string, but on my linear uke I didn't widen it, and there isn't much problem. The low G string doesn't sit completely flush inside the slot, but there are only some minor intonation problems, and those tend to happen pretty high on the neck, at around the 8th fret. Even then, it's not something I notice. Anyway, I'd prefer to have some intonation fudge high on the neck than widen the nut slot, go back to a re-entrant G, and risk buzzing because the slot is now too wide.
Still, if it will be a dedicated low-G uke, I suppose widening the slot isn't a bad idea.