Hugh has been playing on ALL the studio records, including the first single "Runaway" when Jon no longer had a band + on some live albums + he's been one of Obie's close friends long before the 2 ever met Jon so, unless Hugh decides to quit his job (which is very unlikely), there'll be no other bassist, and surely not Alec. Jon holds a big grudge against him and he doesn't seem to be someone to forgive people's mistakes/bad decisions...

There's an old YT interview in which Alec called a radio station to support a politician and he's very harsh towards Jon.
Apart from that, yes, "the dude just fell off the face of the earth"...

If anything, Jon would rather pay him NOT to write an autobiography with lots of "behind the scenes" BJ stories. I suppose he signed a contract obliging him to keep his mouth shut or else I guess such a book would have been published a long time ago, when BJ was at the top of their popularity. Nowadays it wouldn't sell, nobody cares anymore.