I don't want to give up Brock for emotional reasons as I love him as a player and person, but I wouldn't be mad if we got a lot value for him.
If I had to bet on someone potentially declining in the following years, it would be Brock. His physical tools seem like they've diminished since his rookie year and may further do so of no fault of his own (injuries). And yet, he's maintaining a PPG pace as you said as a 22 year old. As a result, his value is EXTREMELY high, but as diehard fans who watch him every night, you can sort of tell that he's not necessarily the same player, and you can have a hint of doubt that he may not ever get his rookie year physical tools back. That makes him a player who you can potentially trade now, and look back and say: "wow we didn't expect that trade to turn out so well."
Again, not advertising it for my own sentimental reasons and none of the above is definitive of course, but if we were to explore trades I wouldn't be mad either.