This is a great idea, you should be selling your alts and getting bitcoin if you do not trust your alts and you should be doing something better with it which is bitcoin. You can trust bitcoin for sure, there is no reason why you shouldn't trust bitcoin, it will go up in the future and there is no way around it, I know that some alts will go up too, but we can't say all alts will go up, some of them will and some of them won't which means that we do not know which ones will go up and which ones will not.

You might be holding one that will go up so selling that and buying bitcoin could be a mistake, but if you are holding one that will go down then it's going to be terrible. This is why you should be careful with what you are doing.