The Tottenham star is attracting interest from Champions League winners Real Madrid, the Daily Mail reports. The same report also claims that the north London club are unwilling to let Kane leave the club, even if they receive a world bid in the summer.
Liverpool legend Graeme Souness has advised the England international to swap Tottenham for Real if the 12-time European champions make an approach for his services.
Rooney believes Kane's motivation will now shift from "goals to trophies" and failure from Spurs to win silverware will force "the best striker in Europe" to leave his current employers.
"At the moment, he is probably the best striker in Europe. He can go where he wants to, he's that good. He is like a young Alan Shearer. He scores all different types of goals," Rooney told Sky Sports.
"The problem that Tottenham are going to have is that his motivation is goals, but his motivation is going to change from goals to trophies. And if Tottenham don't win trophies in the next year, maybe two, he is going to want to move elsewhere to win trophies.
"That is a decision he is going to have to make in the next year or two, but Tottenham have also got to make a decision - bring more players in and have a real push to win the Premier League."
Meanwhile, Tottenham manager Mauricio Pochettino echoed comments made by Rooney and even stressed that only Kane will have to make a decision whether to leave the club to win trophies elsewhere.
"That is a decision he is going to have to make in the next year or two, but Tottenham have also got to make a decision — bring more players in and have a real push to win the Premier League," Pochettino explained.