Lisk doesn't depend on BTC. Infact Lisk relies as much on BTC as Ethereum does.
Lets be honest, BTC in terms of what it promotes, is an outdated coin that is slow and expensive for what it was designed to do. There are far better coins out there. The only real thing BTC has is it's name, which most people have heard of and have some understanding. Eventually BTC will be surpassed by something better.
Maybe, maybe not. The hype around the
BTC name is very large, and the inflation rate and scarcity of the coin cannot be underestimated. It can always be seen as a storage of value, and I think the Lightning network will make transactions drastically faster. But the constant forks are diminishing the whole space. Decred is superior in it's governance. Projects like Lisk can grow somewhat independent of bitcoin.