When LN will be there, will BTC go the moon and crush all altcoins on the road ??
I think that initially, public adoption of Lightning will cause a bear market in most altcoins. It will probably cause a reversal to the falling trend of "Bitcoin dominance." And in the end, I think it will crush any altcoin that has no other selling point than fast/cheap transactions.
However, it's important to note than the altcoin realm is becoming much more diverse than simple payment/messaging protocols. We are talking about decentralized exchange protocols, privacy mechanisms that could take years to implement in Bitcoin, alternative governance mechanisms, decentralized lending, and and other protocols/suites that can offer lots of new use cases that Bitcoin doesn't address right now.
Rootstock did recently launch on Bitcoin. It's in limited release right now (not public), but it's on the mainnet and could offer scalable sidechain transactions and smart contract functionality in Bitcoin. That could cause even more downside pressure on the "fast/cheap transaction" altcoin niche as well as the Ethereum and Ethereum-clone "smart contract" niche. Interesting times ahead!