Given how like Doctor Who Loki the series was, I wonder what the odds are of a Dr Who/Loki crossover? 
Controversial opinion but given I've enjoyed the majority of Disney's MCU and SW televisual output way more than I've enjoyed Who the last few years is their involvement necessarily a bad thing?
That being said I think @Steve Roby is spot on, this is likely a defined, contractual partnership where the BBC continue to own Dr Who and Disney agree to put money into the show in exchange for the exclusive distribution rights to show it everywhere outside of the UK. I'm sure there will be strict rules about what Disney can have input into and what they can't.
So long as the BBC retain the overarching IP I'm not going to worry unduly.

Controversial opinion but given I've enjoyed the majority of Disney's MCU and SW televisual output way more than I've enjoyed Who the last few years is their involvement necessarily a bad thing?
That being said I think @Steve Roby is spot on, this is likely a defined, contractual partnership where the BBC continue to own Dr Who and Disney agree to put money into the show in exchange for the exclusive distribution rights to show it everywhere outside of the UK. I'm sure there will be strict rules about what Disney can have input into and what they can't.
So long as the BBC retain the overarching IP I'm not going to worry unduly.