It's not that mind boggling. If he moves to City next year on a free, wins 2 PL titles and two cups, he'll be remembered more for being the PL top scorer. In ten years time he'll be introduced/branded as the all-time PL scorer. Trophies are obviously important to the legacy of a player/team/coach, but all-time scorer in a league is a singular achievement much greater than what any individual contributes to a title win. Only exceptions maybe Maradonna '86, Suarez if Liverpool had won in '14. A major trophy win will be a monkey off his back to be sure.
It's better for him to wait it out next year, he could literally move to any team on the planet in 12 months, even Real as well which is why I don't think he'd be in a hurry to move this Summer.