KuwabaraTheMan
Banned
Eventually?
Yes.
The show began in 1963. It'll probably continue on. They will recast some of these characters in small roles eventually. It's probably better if you come to terms with that now rather than 5, 10 years down the line. It's like trying to fight reboots.
But it's literally never been needed before.
The genius of Doctor Who is that they can (and do!) replace the entire cast every few years, and continue on just fine. You just have the Doctor regenerate, and you write out the old companions and introduce new ones.
There is no need to ever recast. And it's gotten by just fine without it. When the show hit its highest ratings in decades and reached #1 for the first time ever near the end of the Tennant era, they hadn't done that by getting someone to pretend to be Tom Baker and recast a younger actor as the Brigadier, they did that with a brand new Doctor and new companions (along with Sladen returning in a small role).
The idea that we need someone to come along every few years and pretend to be William Hartnell is silly. The Doctor is always changing, so there's not any need to do recasts. Doctor Who is pretty much unique in that it can get by without ever recasting and still maintain the legacy of those previous seasons.