I feared new altcoins will be left out so i start selling some coins for bitcoin because it can be a big blow if altcoin fails to surge like in 2017 after bitcoin reach a new ATH, what do you think? And what would you have done in my position
Some of your details are accurate. Bitcoin are started to pump and also a good alt coins, For me the chance of new alt coins to be famous has reduce on my side, But it is still depends on their blockchain tech if hows it will be use or more use cases.
when bitcoin is pumping this situation will be very good for altcoin to update. at times like this, the enthusiasm of investors becomes more. but as you say, it depends on how the use of technology and the use of their platform is accepted in the market or not.