Here is my attempt at btc bottoming fundamental analysis:
Bitcoin mining difficulty peaked on 9/30/2018, then went flat, now rapidly declining.
The last time this happened on a sustained basis was during Nov 2011 bottom.
In 2011 it took four months before market bottomed and decline in difficulty stopped (in correlation with the price rebound).
Counting from 9/30, we are already two months into difficulty decline period.
If total decline period is to last only four months, we would need to turn around (price-wise) within a month (or already) to get to the rise again by the end of four months period.
One may argue that it could last longer, but nobody knows what the result of such decline would be on system functioning. Yes, difficulty would slowly adjust downwards and relieve the pressure on miners, but it takes two weeks for adjustment, which might be too slow for some.
IF, on the other hand, you would continue both price and difficulty decline until mid 2019, bitcoin might be in jeopardy by the time it turns around there.
i don't think it makes sense to focus on miners. difficulty may lag a lot, but it should eventually follow price on a long enough timeline. mining costs remaining above price means miners bleeding money---they should eventually shut down. between the last adjustment and the upcoming one, we're looking at more than a 21% difficulty drop, so we're seeing that dynamic in action.
the important thing is when price turns around. that's anyone's guess, but i tend to agree with those who (based on history) believe we're at the tail end of the post-bubble bear market. the closest model so far is 2014. that cycle topped in november 2013 and bottomed in january 2015.