Should we be worried? Should we trade our BTC now for other coin like ETH?
I think now about 75% of bitcoins are mined and very sooner all of the bitcoins will be mined, I think, so then we should have to care that who is mining it. We just have to adopt the bitcoin for our use, in the coming future the power will be with those who have adopted it.
Better if you will stick to bitcoins as all people do now. Waiting patiently for bitcoin halving, there is a possibility that bitcoin will be destroyed, but as of now it is still on the go and having its fluctuation.