Yes, but it still doesn't happen overnight like you're suggesting. You probably still need 4-5 years until you're a serious contender for an NBA championship.
Tanking won't work in Toronto. Fans won't come to the games and as well it'll even be a lot more tougher to sign FA's or keep players here. It's better that the Raptors stay relevant even if that means coming in 4th or 5th and getting eliminated in the second round for 2-3 years after KL leaves. Because when a player like KL or AD become available with one-year left on their contract, you likely will able to swing something and greatly improve your team. We're talking about the East here which has been pretty weak for some time. Even after KL leaves, there is no reason for the Raptors to tank. They still have Siakam, OG and Freddy, along with solid veterans in Lowry, Ibaka, Gasol and they likely will re-sign Green. Masai could get creative again and make another trade this offseason to bring in a solid player to replace KL. As well, might be able to sign a middle-tier FA that could help as well. If the Raptors didn't have Siakam and OG, and if Lowry and Gasol were in serious decline, then sure blow it up.