Depends. I don't foresee it being much more desirable to attack Bitcoin, even if the hashrate of the network drops significantly. The profits gained from an attack is far lower than the cost and the complexity of its execution and double spent Bitcoins can potentially just be worthless still.
What if the attack is not due to profit motives? For example, Governments perform an orchestrated attack or some mega rich trillionaire is bored and wants bitcoin gone.
It ultimately depends on what you mean by "Bitcoin gone". If you are new and have only known bitcoin to be one of these 8 thousand others claiming to solve the blockchain trilemma, you'd be forgiven to think that bitcoin is just the most expensive coin. For someone with this motivation, a trillionaire (are there any), or a Government can surely reduce the fiat value of bitcoin and for them, bitcoin will be gone.
For those of us who love it for the sake of the network, the community, the legacy, the development and sheer audacity of its pseudonymous founder who embed a message for the world's most powerful lobby of people in its genesis blocks; for those of us, the network will never be gone, Bitcoin will never be gone.
This is what started it all. Just one lone cypherpunk convinced by the code of another one, "Running Bitcoin". This just goes to show that Bitcoin can never be gone till there are even two people who agree that it ought to run. And there are millions of us today. This is something you can never replicate with all the corporation/ foundation coins and their figureheads bamboozling newbies with jargon.