Magnus 2882 ELO = Most Likely Peak Human Capability

That's not to say Magnus doesn't have the talent to break 2900 but more than likely will never do it because there's nobody there at that level with him to compete against and push him. FIDE would have to rework their rating system, inflate those under him to get them closer to his rating so that he can earn ELO off them. Meaning they'll need to fudge the numbers to make this happen.

2900 classical ELO is technically achievable but statistically improbable in the current system.

+3000 would probably require Human/AI (Technology) integration (think Cortana inside your head like Master Chief); then everyone would be super human at chess and there will be little difference between the absolute best & the mediocre.