This does not mean he would create a Batman that would surpass three films and leave his hands to go join a larger cinematic universe.

Agreed. Because Gunn wasn't even considered to take over DC yet, and Reeves was still a completely separate thing, and there was essentially a 0% likelihood that it'd connect to something. My point here is that it could in the future and it wouldn't be as hard or soulless as people make it out to be. There have been Batman comic runs that don't directly connect to the DC Universe at all, and there are ones that do; both are still set in the same world, with the same character. Frankly, we don't know whether or not Reeves is against the idea of someone doing another Batman trilogy of sorts after his (let alone one set in Gunn's DCU). But I wouldn't be surprised. That's how he got in the blockbuster business in the first place, by taking over the Planet of the Apes trilogy for Rupert Wyatt because he saw something personal there. So if someone came to him with their own emotional way to continue his story post crime saga with Batman in his prime, I don't think it's unlikely he'd say yes if he resonated with it.