The typical 8-string pickups are custom-winds from here and there, EMG 808s (which are... you guessed it, 707s with one more string), and Lundgrens.
I don't know what you mean by 'trend', but extended-range guitars aren't going anywhere and there are more than a few people - myself included - who are just waiting for affordable 8s to come out. There's a lot you can do with more notes... if you don't need them, don't get them (I'm looking at you, nu-metal), and hopefully I won't have to strangle someone for saying that everyone who doesn't play a 60s Strat with 50s strings into a vintage Super Reverb sucks and should just stop playing.
Oh, and while rumors abound of DT with an 8, I'm sure people like Dino Cazares are going to be more of a driving force... not only does Devin already have all but one note of a 8-string with his 7-string Open C/G tuning, Dino rips the fuck out of his on a much more regular basis.
Jeff