Is the Tavor enough less modular to matter? It could be converted, fairly easily, to any caliber an AR15 pattern rifle could shoot.
The cost? Yes, certainly replacing every single rifle in the US military would be a huge expense. Why do that though? Why not convert on a unit by unit basis? That's what the Israelis are doing.
I dont think it is a caliber modularity issue but a sizing one. Cant effectively adjust the LOP on the tavor. The problem with converting on a unit by unit basis remains cost. Still have existing inventories that aside from barrels and springs are mostly reusable into pretty much the foreseeable future, barring breaking them. The Tavor while an awesome rifle is hardly a revolutionary change from the AR. Is it really worth transitioning to a new platform with new labor skills needed tooling and training all the while just throwing away perfectly effective rifles?