Long-term viability of assets stored on Polygon PoS

Given that the Polygon PoS will soon have to compete with far more secure L2 EVM solutions, such as ZK and optimistic L2s from Polygon itself, I’m wondering what will happen to assets such as NFTs that are created on Polygon now.

It seems like, at some point, the PoS will be so obsoleted by rollups that have similarly low cost, but more security, that it may be that no one wants to use Polygon PoS and there might not be active validators.

What happens to assets that were created on Polygon PoS before that point?

Would it be possible to to use the checkpoints stored on Ethereum to prove that those assets are in the Polygon PoS even if there aren’t a sufficient number of validators for the chain to still be considered to be active? If so, how would that be done? Is the process runnable now by a concerned user to test it out?

Or will there be extremely low-cost bridges to move those assets to a L2?

I understand that there’s a bridge now to move Polygon PoS ETH, ERC721, and ERC20 assets to Ethereum L1. But it doesn’t seem like that will ever by cheap to do, so it doesn’t seem like a viable solution for assets that have relatively low individual value.

[Update: I found someone on Reddit saying: “AFAIK, the checkpoint does not support fraud proofs nor does it reconstruct the chain. What it does allow for is social consensus to restart from an agreed base in the event of a hard fork.” Does that accurately sum up the situation about the checkpoint?]