The Bitcoin Halving means that if the price stays the same, the money that can be spent by miners halves. Everybody expects that this will double the price. (although it could be already included in the current price of Bitcoin).
It could be a self-full-filling prophecy, as many speculators just enter Bitcoin as it holds the longest track-record and they do not really understand what a blockchain is for. They buy it and hold it on exchanges. They do not experience the shitty transaction times and other problems of that blockchain.
Bitcoin could be easily attacked, for just about 600,000 USD/hour costs. After the halving this will drop to 300,000 USD/hour.
Are there not enough enemies with billions of USD which could pay that easily?? A 100 billion USD is very badly secured if one can attack it with a few million USD every now and then, disrupting the utility of that blockchain.
I expect such an attack to occur some day... it would not surprise me...