two developments which are currently ongoing are Eltoo and Channel Factories. In short, these would allow multiple users to cooperate to make a single on chain transaction, and then on top of that single transaction open as many payment channels between each other as they like. This would significantly decrease the on chain footprint of Lightning channels.
What if the channels have to be (force) closed? If that still requires the same (high fee) on-chain transaction, it solves less than half of the problem.
I had to search how it works:
Channel factories are a multi-user contract capable of opening payment channels without putting the channel-open transaction onchain.
For example, three users create a channel factory by each of them depositing some funds to an onchain 3-of-3 multisig address. Using non-broadcast (offchain) spends from that address, they open payment channels with each other (e.g. Alice↔Bob, Alice↔Charlie, and Bob↔Charlie). They can then use those channels with the same security as if they had opened them onchain because, if necessary, they can broadcast the channel-open transactions. However, they don’t need to broadcast those transactions if both parties act cooperatively, allowing them to reduce the amount of block chain data used.
For large numbers of users under ideal situations, channel factories can reduce the onchain size and fee cost of LN by 90% or more.
This sounds like a potential disaster if one of the people no longer cooperates and both the opening and closing transactions need to be broadcasted at a moment when on-chain fees are very high.
