I have heard this rumour as well. maybe this American FTO intends starting where BAE left off.
As far as I am aware BAE moved to Spain, among other reasons, because the good old British weather caused to many interuptions to their flight training. I have also been told that the lack of an alternative runway and the regularly high temperatures at Jerez (above 35) cause BAE more lost time than they ever had at Prestwick.
There is certainly a market for commercial flight training in the UK so if an american FTO wanted to expand their business why not tap into the space left by BAE and train at Prestwick which has been proven as an excellent location for comercial flight training.