is this the right moment for pick altcoins with BTC
Yes.
what do you think will be the lowest price in this summer ? wait more =?
Price for what? bitcoin? if you're asking about bitcoin it should be $7,500 down to $7,000 and that can be the bottom price for it.
It is a splendid and nice idea but buy the altcoins that you think have a good profit in the future so that you don't waste your effort and investment.