pointed out and @JBanton
has shown with the link, this isn't late breaking news. I would go as far as to say it shouldn't have been a surprise either given the path the industry has taken, the precedent set by GT Sport, etc.
More and more titles are moving to an always-online model especially those that cross over progression, achievements, etc. from their campaigns / solo elements to their community online ones. .....for obvious reasons like mitigating cheating.
Having said that, I get why some prefer offline due to their situation with their online service providers (e.g. caps, quality), etc. but as I see these petitions for more and more games, the reality of it is that the impact simply isn't big enough to change developers minds I'm afraid.
I'm sure arcade will still be available offline as (IIRC) it was in GT Sport, but I'll wager they will not budge on making other elements offline to in GT7 or moving forward for that matter.