I don't know why people are assuming that the entire of Naughty Dog are working on this, if you're. Remakes don't need as many people, especially if Naughty Dog are using the same engine (albeit upgraded) for TLOU2 as used in the original TLOU, which I imagine is extremely likely.
In that case, port over to the upgraded engine, bring the gameplay up to par, upgrade the textures, visuals etc. I'm not saying it's a small or trivial job, but it's probably like a 50 person project at ND to "remake" it, alongside porting TLOU2 to PS5. It's nowhere near the type of work needed to make TLOU2 from scratch.
There's enough people at ND to have another two teams working on full games alongside that. Hopefully one team is working on a new IP and the other is working on the MP game, with one of those teams likely to move to TLOU3 after they are done with their current project