This would be nice if it were true.
If its for Hayward, we get a cheaper player for an extra year who is just as useful, and just as good. Brown would have to play more 3/4 but he's great at that defensively, and will probably score more easily against bigger players.
If its Kemba, that's most likely the best case. We get bigger and tougher and close up a defensive weak point with a great defender. Holliday is actually a little better passer/facilitator too. He's just not quite the scorer, but that's fine. He's more than good enough.
If its Smart and parts, that might be just as good or even better if Kemba manages to come back at full strength. Not too big of a drop off defensively, a huge boost on offense, and a much calmer guy.
It's hard to see this as a bad trade. Holliday is very good, defensive minded, provides size and athleticism at his position and is a great teammate.