It is very hard to look in the future, especially when it comes to crypto currencies. But generally, I did not mention that any new altcoin has effected the prices of the old ones. Furthermore, there were no projects that truly succeeded.
Of course, old coins are unbeatable as it has a good number of investors and so many supporters are holding it still in the market. Altcoins are good to invest your money but only old coins are good otherwise people are showing a lack of trust for those coins which are new in the market and yet they dont have a number of investors in it but with the passage of time it all will increase.