The important thing to understand about Lightning is that when all transactions happen off-chain, miners don't generate fee revenue. This undermines the security and sustainability of the network, which is all based in mining profits. With each halving event, miners become more and more dependent on transaction fees, until the subsidy is removed entirely and transaction fees is the ONLY income miners will generate. It's a ticking timebomb under Bitcoin - scale or die.
Miners don't just secure the network out of the goodness of their hearts, it costs a lot of money in electricity. This is the paradox of a system like lightning - it is supposed to enhance Bitcoin by making traffic happen off chain, but instead it undermines all the economic incentives that make Bitcoin work to begin with.
Could you tell me - why am I wrong?
If all transaction happen off-chain,Bitcoin will NOT be Bitcoin.It would be simply dead.
If there are zero transactions on the BTC blockchain,miners won't generate any revenue from fees,therefore they will quit mining.If there aren't any on-chain BTC transactions,the market liquidity of BTC and the demand for Bitcoins would be close to zero,which means the Bitcoin price would be close to zero as well.
I don't think that the majority of the Bitcoin Core diehard supporters actually trust the Lightning Network project and would start using LN in the future,so your theory simply won't happen.