Lukaku has also not decided on the club, Fabrizo Romano tweeted that Juventus are ready to give Lukaku 37.5 million euros + 2.5 million euros in bonuses, and Lukaku has already negotiated with the club, but this will only be possible if if Juventus sell Vlahovic. Inter are not happy with this state of affairs, as they still have not received any response from Lukaku regarding the completion of the agreement.
Yes Juventus must release Dusan Vlahovic to another club if they want to sign Romelu Lukaku. So far there have been several clubs interested in Vlahovic such as Chelsea and Arsenal, it's normal for his age and prospects to have very promising in the long term. However, if this option works, Juventus will reap losses by releasing potential young striker Vlahovic by recruiting Lukaku from Chelsea and having to make a bidding war with Inter Milan. Considering that Lukaku is 30 years old and Vlahovic is still 23 years old, I think from this point of view that Jeve was wrong in recruiting players even though he had the advantage of letting Vlahovic go.
It is true that until now there has been no clarity regarding Lukaku's contract, Inter Milan has not been able to meet the price desired by Chelsea's management, The Blues want Vlahovic to be an option for Juventus to hijack Lukaku from Inter Milan.
I understand that Chelsea may want some decent money for him, but to be fair at his age and after his injury, they are not going to get a huge paycheck for him. Whatever was offered could be the fair deal and I feel like that's the deal they should take. Chelsea is not lacking money, they have sold some big names and have some good players, I feel like they could use that money to buy whoever they want.
Between other sales and Lukaku sale, they will have enough money to buy Vlahovic if they want to. Plus, you can't expect these two players to be close in value neither, it is going to be a bit of a tough deal. I hope that people could end up with a good situation in the end but until that happens we aren't going to see much change.