My understanding is that all/most built in batteries are interchangeable (I may have that wrong).
They can be removed and replaced by a competent person..... which lets me out

or at your LBS.
One of the reasons I am looking at Cannondale is that the dealer is local
The battery case is bespoke, so if the company folds a replacement may be hard to source.
However, it uses standard Samsung cells, so it should be possible to recell it, provided the case can be opened and closed without wrecking it, and provided the software doesn't brick itself if the cells are changed.
That's unlikely, although Bosch bikes cannot be recelled for this reason, even though they use the same widely available lithium ion cells.
mm - cannondale - been though several ownerships - god knows who owns them now - for a while had no British representation - I had a very nice expensive dale with clever suspension - had increasing issues getting it serviced - ended up speaking to a dale bod in the netherlands who basically said scrap it - said that I surely wouldn't expect to get bits/servicing for a car of that age (10 years maybe) and would surely just scrap that. Not true for cars of course and I found his argument bizarre and terrible.
I wouldn't touch anything by dale now.
It is a wonderful frame though - excellent welding of the ally. Done in the states I think.
It was always said the American made and welded Cannondales were better than the Far East ones.
I believe Cannondale still make a handful of models at home, but most are outsourced.
From Dave's point of view, I can't see any reason to think a Cannondale ebike will be any better or worse than the other major brands.