With the upcoming v0.15 update for Monero, unencrypted payment ids are going to be removed. But what happens if someone sends to a Monero address using one of these payment ids? Would the coins be lost since payment ids aren't supported anymore?
The Monero wallets, from v0.15, will no longer allow transfers with an unencrypted payment ID.
No coins will be lost in an attempt to use these unencrypted payment IDs; the sending wallet will simply report an error explaining that unencrypted payment IDs are bad for privacy and abort the transfer.
The short, encrypted payment IDs can still be used (such as the ones in integrated addresses), so either use those or better still, use subaddresses.