Seven 788s have been converted or are in the shop at PAE for refitting (out of 22 788s). Practically, as N800AN was the test / trial article last year, it means AA is moving quickly on this retrofit of PE (and concomitant reduction of Business seats). For once, it looks like a stated deadline (June) will be met, and it has been reported that AA is only selling 20 Business seats on this aircraft.

I’d strongly recommend avoiding booking a seat in the row 6 or 7 mini-cabin. Even if the older aircraft version shows as one’s flight, an equipment change from a 28 to 20 seat cabin could occur - and the odds are increasing that could happen. Reference threads:

Boeing 787-8 / 788 Premium Economy / PE / PEY progress and seat info

AA limits 787-8 / 788 Business seat sales to 20 (One Mile at a Time)