The only thing we know for certain is that Rom has said he isn't going to sign the contract that is on the table, and that, at the end of this season, there are 2 more years remaining on his current contract.
As I see it, there are 4 possible outcomes.
1) The club offer a revised contract that is acceptable to Lukaku and his agent. I can't see this happening to be honest, and I certainly wouldn't welcome it if it meant putting the club in worse position than it is now as regards future potential transfer fees.
2) The club shows ambition early in the transfer market. Brings in he likes of VVD and Tielemans and Mertens. and Rom decides he's seen enough commitment from the club and decides to sign the contract on the table. As an optimist, I'd like to believe that this is a possibility but the cub need to be a lot more decisive than they have shown in the past for this to happen.
3) The club will have a value in mind for Lukaku which I suspect will be north of £70m. The club will also want any business does early in the window, certainly by end of July I would imagine. Rom and his agent will be aware of all this. If somebody comes in and offers the required amount, then Lukaku will go. I believe this will be the most likely outcome.
4) No club meets our valuation of the player so Lukaku stays with us. I think this is the second most likely outcome and I'm not sure how I feel about it. Depends on how the player commits himself on the field next season. We've seen both sides of Rom during his tenure here and I don't know which player we'll see if he is forced to stay.
As for which party has the upper hand, I actually think it's 50/50. Yes, the club can force him to see out at least another year of his contract, but by doing that his value will undoubtedly drop plus we may have a disgruntled player on the books. From Roms side, he can also decide not to sign for a club if he so wishes. So if the likes of a Chinese club or PSG match our value, Lukaku is not compelled to sign. In addition, from the end of this season he has a limited period when he can invoke FIFAs article 17 which allows him to buy out his own contract. It's very rarely done so I'm not sure what the actual process is and how long it takes, but it will undoubtedly be very unsavoury for all concerned.
As regards potential suitors for Rom, it really is a limited market. Apart from the Chinese, there are probably only 6 premier clubs, 2 from Italy, 3 in Spain, 1 in Germany and 1 in France who could afford the fee. So 13 in total. He won't suit the style of either Liverpool or City and I would say the same for Barca, Real Madrid and Munich. I don't think Arsenal will provide CL football and I don't think he'll be happy playing in a sub standard French league. Spurs already have Kane plus I don't think Levy would be prepared to pay the fee. Juventus have Higuain, Dymbala and Mandzukic. That leaves United and Chelsea in England, and Milan and Atletico abroad. Not a great deal of options for him and it's highly unlikely that Milan will manage to catch up with Napoli for a CL place so that will probably rule them out too.
Bottom line is I've really no idea what is going to happen in the summer and we'll just need to see how it all plays out. This is reflected in the betting which actually has him staying at Everton as slight favourites ahead if joining Chelsea and Man Utd.