>>96384173Slott has made it abundantly clear he has no intention of leaving willingly. The only way he's off the book is if he's booted off, which'll only happen if the series drops to panic level low sales.
What's panic-level low? That's a magic number only Marvel Entertainment will decide on. I'd guess around 45-40k (around the same level their B-listers like Thor are selling at), but even this is no real guarantee. They might just try to artificially boost sales again via a relaunch (Marvel's MO for a failing book, as seen with Captain Marvel), event, or an ace-in-the-hole story arc (Five bucks says they bring Gwen Stacy back).
And remember: this is all under the incredibly optimistic belief that whoever they bring on next would be a good writer, that Marvel would be willing to roll-back on the changes Slott's made (when Marvel has always reacted to negative reception with doubling-down), and that they're overall willing to learn from mistakes.
>>96384188At this stage, this' pretty much the only reason I can think of. Slott's staying on either due to the stubborn belief that he's 'still got it', even though he clearly doesn't, complacency, and/or the desire to put his name in the books as the first writer to have a decade on ASM.