If Sanchez is to leave Barca i can only see 2 clubs he would choose -
Juventus - Maybe he really loved the Italian culture and would love to live there again
United - Joining a club that can only go in 1 direction after last season, exciting times - an apparent United fan as a child.
New manager, New players, New ambitions. Highly likely to be back in the CL next year.
Teams i dont believe he will join
Liverpool - OK they got CL football this year but are on the verge of selling the main reason they qualified for the competition to Barca. A team built around an aging Gerrard who will be finished in a year or 2. A team that possibly wont qualify for the CL again next season without Suarez.
Arsenal - Highly unlikely to mount a serious title challenge for the duration of a season. A club that when they are in with a shout of winning the league and need to buy a striker - loan an old, injured, Swedish has been midfielder. Ambitions of finishing 4th every year but nothing more.