It will take much more time to get ETFs made for other cryptocurrencies aside from bitcoin. The main reason why the BTC ETF has gained more potential is due to the launch of futures contracts last year. This instrument helps traditional institutions gain access to the asset without actually buying it and that will help the development of the ETF and it creates the opportunity to accumulate correlation to the asset without having to be concerned about wallet security and/or custody. The only other potential asset to get an ETF right right would be Ethereum given its market cap and broad distribution but still unlikely because of the lack of a futures market which should be close to being launch as well.