From the other side of this equation, my DP has been talking about us living together “a lot will change in the next 5 years” since we met 8 years ago!! To be fair, we both have our reservations, so we haven’t made it happen.
His DDs were trying to push for him to get them a dog, and it did bother me, as it meant that if we DID move in together at some point I’d have to live with a dog, which I hate, and I know that their dog would be poorly trained, as I he wouldn’t put in the time and discipline to train it well, so it would be one of those jumpy up, barks at everything, sleeps in the bed type of dogs!
(Plus I know he would never pick up the poop) and I’ll be honest here - even though he decided to get kittens instead - it stings a bit that he’s able to make a 15-20 year commitment to live with an animal when he hasn’t made one to me. It didn’t help that their mum was helping them in the search for these kittens so it felt a bit like they were getting them ‘as a family’ too.
It may be irrational and of course it’s your house, your choice, but if he’s actually being honest about wanting a future with you, this dog becomes part of that so he should at least be somewhat involved in the conversation rather than you just telling him it’s happening, as this dog could become part of his household too. FWIW when I was doing online dating, I would rule out anyone who had a dog in their profile as I just didn’t want to end up with my life revolving around a smelly dog.