If the bitcoin does not increase block size or the transaction is congested, the price of altcoin will rise a lot.
I agree with that. It is the reason why many altcoins are rising fast.
My be it is a valid reason,because when ever new people enter the alt coin market,they see the price of bitcoin really high and i do think they will hesitate to invest in it and they would scout for alternatives and so is the reason we are seeing huge rallies in all the coins,when it comes to Zcash to reach 0.2 btc means an increase of 100% from the current valuation ,which i think is impossible at this stage .