The biggest issue is whether transactions fees alone will be enough to sustain the needed hashpower to secure the network.
Not tested. Nor can we accurately predict it without making certain assumptions.
This is generally no big deal when current block rewards are 3.125 bitcoin each. The fees are a nice bonus, but they don't make or break bitcoin miners as of today.
We are not talking about today, but when block reward ends and fee becomes the only driver.
One thing I'm sure of is that the likelihood of all miners living Is extremely low
We have difficulty adjustment Incase there's a reduction in miners which would increase those remaining profit
And in turn may attract in more miners.