Obviously Sancho has great stats in Germany so I would think that his next club will be Bayern as over the years they have tended to pick the best players from Dortmund and they have carried their form with them.
The players that have left Dortmund and moved to another league have been disappointing to say the least, Perisic is the only player that comes to mind who has done well and that is in the slower paced Italian league.
Spending big money on Sancho to bring him to England is a huge risk in my opinion and if we have any sense we should leave it to another club to take that chance and get burnt, Kagawa and Mikki are far from being distant memories.
De Bruyne is another player. So is Sane.
1. Kagawa
a. 17 goals 14 assists as a 22 year old ~~2 dribbles per game ~~3300 minutes
b. 12 goals 2 assists as a 21 year old ~~1.3 dribbles per game~~2100 minutes
2. Mkhitaryan
a. 23 goals 32 assists as a 26/27 year old ~~2.6 dribbles per game~~4300 minutes
b. 5 goals 7 assists as a 25/26 year old ~~2.6 dribbles per game~~3100 minutes
c. 13 goals 10 assists as a 24/25 year old ~~3 dribbles per game~~3700 minutes
3. Gotze
a. 7 goals 8 assists as a 19 year old ~~3.5 dribbles per game ~~1700 minutes
b. 8 goals 16 assists as an 18 year old ~~2.5 dribbles per game ~~3000 minutes
Sancho
a. 14 goals 15 assists as a 19 year old (mid season) ~~3 dribbles per game~~2050 minutes
b. 13 goals 19 assists as an 18 year old ~~3.3 dribbles per game ~~3000 minutes
Based on age, rate (per game), dribbling, and end product I would argue that Sancho is #1. And he's 19 years old. You wouldn't need him to replicate his stats over in England. If he produces at 3/4 of those stats when he's in his prime, that would be a huge success. You should look at his age and his performances in Germany as a development stage for him. This is not even close a comparison in leagues (so don't take offense German fans), but if you were to take a Championship player doing well as a 19 year old, and then buy him, sure he won't hit those same heights initially (hello Zaha), but he will grow in ability that he will eventually start to produce at that level in the tougher league. Not sure why Sancho isn't the same.
On the other hand, someone like Mkhitaryan was already 27 years old when he came to the PL. There was no more development left for him. Completely different from Sancho's situation. Plus, look at Mkhitaryan's other seasons in Germany. He looks more like a 1 season wonder when it comes to that kind of end product.