This chart shows when the 2017 peaks of the ETHBTC, BTCUSD and ETHUSD pairs happened. Notice how casual the ETHBTC top appears on the BTC.D chart. When Bitcoin rallied to make its top against USD, it also rallied in Dominance. A few weks later it was Ethereums turn and then the cycle concluded.
In June 2017, the ETHBTC valuation reached its highest value. Half a year, before ETH und BTC peaked against USD. The situation this year might be different, but I want to gather some possible indicators nonetheless.
A marks the top
B marks the bottom
C marks the height of the previous cycle top
Red: Halvings
Green: Cycle Tops
Take a look at the RSI. It doesn't look completed yet.