How many times do I have to make the point that I have repeatedly above. Clearly then can do whatever they like should Roman be hap[py to fund it. As it stands Mourinho seems to have made it quite clear he (and other unhappy players) can leave if they wish. The fact that he's been limited to signing Eto'o rather than the blockbuster forward he wanted suggests he may need to move players on before he can spend any big money, rtaher than have big name players in the reserves.
Chelsea may well not want to sell him to another side in the PL - and they may try to move him on elsewhere. The club wouldn't know unless and until they tried. If they make a decent offer to Chelsea and the player wants the move then they might let him go.
The fact is, United are unlikely to be direct rivals this year. I suspect neither Real or Barca could fit him in. PSG may want him but he might not fancy that. I suspect Arsenal, Spurs and United might be interested and of those United might be the most paletable for Chelsea as it stands.
At the end of the day its all speculation but Chelsea have a player worth decent money who the manager has made clear he won't pick - there seems no way back for him as he's done nothing wrong, the manager just doesnt fancy him. If another side wants him that might mean Jose can get the forward he wants.