Good stuff. I enjoyed this write-up as my thinking has been inline with this (confirmation bias at its best).

I would hesitate to say this is "risk free" through the upcoming fork(s). After the returns we saw on and after the BCH fork many may be front-running this trade.

It's clear that the increase in BTC has been aided churn within the ecosystem. On days BTC has been up 10%, alts have been down > 10% vs. BTC so it's not just new money being introduced. Which says to me this has more to do with timing the fork(s) than it does with adaptation by new entrants.

There have been a few alts that have been very resilient to these swaps, so that may be a method of analysis. However, as your title states, timing is everything. To trade effectively you need to be right twice, once when you sell, then when you buy back (then overcome fees).

Good luck.