Good question. BCH has better availability (+timestamps), but for a small fee. Tips create interesting opportunities. IPFS is cheaper, though less performant and censorship resistant.
Could IPFS adopt timestamps and tips??
Not that I know of. The main difference is IPFS like torrents requires altruistic seeders. Content can disappear if no one is seeding it, or have slow seeders. BCH will always be fast.
Users could even pay BCH so their content is well hosted (seeded) on IPFS. Since Memo is text it's worth the fee to put it on-chain and have it hosted indefinitely.
Well...even it is on chain, it does not ensure it is hosted forever. It can be pruned.
OP_RETURN outputs get pruned from the UTXO dataset. They are still required to validate the entire blockchain and are therefore recorded with the same level of guarantees as all txns.
