Bitcoin seems to be the past and Ethereum the future.
The question is :
when BTC will worth almost zero? Next year? In 2 years?

Probably never!!!!!
Why?? Answer is very simple. Ethereum is a hyped coin and when the hype settles/gone then it's value is also gone.
Why i don't invest in Ethereum is that because of its
infinite coins to be mined which is a major drawback according to my strategy.