FAQ: Will Seraphis result in a chain split, with "Monero old" and "Monero new"?

It's possible, but based on past experience looks unlikely.

It's possible that the Seraphis hardfork turns out to be contested: Maybe some sizeable subset of Monero users, miners, and Monero-supporting third-parties like exchanges won't agree to go forward with Seraphis and Jamtis and prefer to stay on the "old" chain after the hardfork indefinitely.

If this happens the result will be two networks with two blockchains and two distinct cryptocurrencies, a true fork instead of merely a "network upgrade".

With previous Monero hardforks this did not happen because the overwhelming majority of users decided to switch to the new software to be part of the new network. While there is no guarantee this will play out the same way with the Seraphis hardfork, a split looks unlikely if the Monero dev team manages to keep delivering solid software and to execute the hardfork without disruptions.

More Info

A recent example for a contested hardfork was Ethereum's switch from PoW to PoS with a hardfork. The "people left behind" continue to run "old" Ethereum which got renamed to EthereumPoW.

There once was a Monero hardfork that was contested to some degree: Monero hardforked to introduce a change in its PoW algorithm, and a group of people behind ASICs supporting only the old algorithm tried to keep the old chain alive, to avoid loosing all their investments in that ASIC hardware. The result was Monero Classic. That cryptocurrency never gained much traction, however.