Yes, I am starting with that assumption, which I did not come up with, but was responding to.
Even if Bitcoin was mainly used as a store of value, you'd still have people using it either for short term or for long term storage.
If used for short term storage, there would still be enough transactions to pay for mining fees.
And the basis of this is what? According to this paper https://www.cs.princeton.edu/~smattw/CKWN-CCS16.pdf transaction fees are not going to be enough to support the network.
I disagree with this because if altcoins turn out to be superior to bitcoin in terms of store of value, then people will shift out of bitcoin, not buy altcoins in addition to bitcoin.
But this is not sustainable. Imagine bitcoin prices continue to increase and eventually all the coins are mined. There are not many transfers because people are mainly hoarding. Thus not much transaction fees, which is the only source of income for miners. Hash power reduces dramatically, and so network security deteriorates.
It seems to me that the only solution would be for bitcoins to be perpetually made available (no limit at 21 million).
If your saying increasing the supply is the solution(correct me if I am wrong, that won't be happening. First, the Bitcoin was set to only be 21M and Second, increasing the supply will mean decreasing the value of it in the market which I think all of the investors will not agree with.
You have it backwards. If it is ONLY used as a store of value, and the supply is limited to 21 million, then the value on the market will decrease, possibly going to zero. The only way that bitcoin can survive is to increase their supply. Read the above posts in this thread. What people think is going to happen if they increase the supply is irrelevant. The market wins in the end.
Of course it is always important to consider what people would think if the "VALUE" would decrease because of the increase in supply. This had been proposed long before but the public have not accepted because it will surely undermine the market value of BTC.
You mean the bitcoin public have not accepted it, not the general public. But the bitcoin community is very insulated in terms of economics and exposure to any ideas outside of crypto. It "surely" does not undermine the market value of BTC.