They had a rule for the first three seasons where Sam wouldn't really leap into anyone famous, but there were some adjacent leaps like where he inspired "Stevie" to write about a killer car. But in the final season he leaped into Elvis and helped Elvis get discovered, Marilyn Monroe's chauffeur to make sure she didn't kill herself before her final movie, and then the JFK episodes. The series always had a different future than reality and the things Sam was changing were aligning it to real history.
Ahhh, yes, that seems familiar.
Anyway, with todays focus on serialized content I'd be very surprised if they kept it episodic and self-contained instead of foisting fourth cousinon his mothers sidean elaborate future storyline on to it and minimizing the amount of "past" content, even if they stick from 1985 to now or however they are gonna do it.
I bet we can already predict who they will mess with.
Steve Job('s personal assistant)
Jeff Bezo('s neighbor)
Tu Pac('s fourth cousin on his mothers side)
Charlie Sheen (in the "very special 'don't do drugs, kids" episode
Princess Diana('s paparazzi, oh, WOULD THEY DARE!!!)