The 21-year-old has impressed Waddock during his trial spell at Adams Park but the Chairboys boss admits the in-demand right-back could be tempted by a more lucrative move to one of three former Premier League clubs who are tracking him, Leeds, Southampton and Charlton.
Waddock said: “Marvin has done well and we will know by early next week if we can do anything.
"He has settled in well and played well. He found early part of training difficult but he has coped and now you can see he is fitter and stronger.
"If we can get him that would be great and if we can't then we have done well for him. I have known Gordon (Bartlett, Stones manager)) for a long time and we want to do it the right way.
"I have a lot of respect for him (Bartlett) and he has done a magnificent job there and we want to do it right but it has to fit for both parties."
Wherever McCoy, with the aid of his agent, chooses to play his trade next season he will fulfil a burning ambition to return to the pro ranks after he was released by Watford three years ago.
McCoy came through the Hornets ranks with former Stones loan players Theo Robinson (Huddersfield) and Harrow-born John-Joe O'Toole (Colchester United) and has been desperate to follow them and his one time shirt rival, Callum Martin (Crewe Alexandra) into the Football League.
Speaking to the Observer in May, McCoy said: “I believe I can play at a higher level but I have to keep my head down and keep improving for that opportunity to come along. It is my ultimate goal to be a professional footballer again and hopefully I am the next one who will shine.”
Stones boss Bartlett, said he did not know if a deal had been agreed.
“Marvin seems to have done very well so good luck to him,” said Bartlett. “The state of play at most pro clubs at the moment is they have very limited finance, hence the reason it is taking Gary so long to make his mind up. Until they speak to us we do not know what the situation is.”
Meanwhile, Stones will play Hayes & Yeading United in a hastily-arranged friendly at Brunel University on Saturday (10.30am).
It will allow Bartlett to have another look at trialists Kurtney Brooks (ex-Watford) and Austrian goalkeeper Roman Pechhanger. as well as involving Chris O'Leary and Greg Ngoyi, who both missed last Saturday's 3-1 friendly defeat at Chalfont St Peter.
Scott Fitzgerald opened his Stones account with a sublime 20 yard free-kick before a fresh second half XI succumbed to some slick Saints counter-attacking.