I think the most likely outcome in the event that the UKGE is cancelled is that MSO will hold the Carcassonne championships at their annual event held in London.
I can't remember when it was last year, but their event runs over 3 or 4 days and includes a lot of very competitive games such as Chess and Go as well as the likes of several Euro Games including Carcassonne. They also have a speed reading event and other disciplines with a big mental aspect to them.
I'd be surprised if anyone would see an online competition as a viable alternative, but if it were it would probably have to be held somewhere like Boardgame Arena which could facilitate something quite easily.