The anime won't survive without Ash. Sure there were endless annoying assholes saying "We need a new protagonist." but you know none of those people actually watched the anime because if they did they wouldn't be trying to overhaul the central character. And they won't watch this new series either. They may tune in for the first few episodes of the new series out of curiosity but if they weren't into the anime before there's no reason they would be into it now just because there's new characters.
The people who make up the actual anime fanbase are where the money is and they love Ash to hell and back, of course they do, it's his show. They've invested so many years or even decades into Ash's journey that they've completely bonded to him. There's no way they will ever be able to feel the same sentiment for another protagonist. Even if these new protagonists last longer than Ash, Ash will always be "the first".

The only people this new series will truly appeal to are children so young that they haven't had the time to become attached to Ash and that's a small demographic with little to no disposable income who may turn out to not be that interested anyways.

My prediction is this new series will do alright in the beginning but it will never achieve the phenomenon status the original did. Then TPC will notice it's not pulling Ash numbers, cut the funding, putting it on life-support and probably turn it into even more of a toy commercial than it already was in an attempt to make it profitable again.
That or they axe the new protagonists and just do a reboot with Ash as the protagonist again in an attempt to cash in on nostalgia bucks.

Either way R.I.P. PokeAni