currently there are mormon temples in quilmes, liniers, and ciudad evita- all conurbano barrios where lower income people live. but all, technically, suburbs. I see the poor teenage mormon "elders" fresh from utah, wearing their polyester shirts and clip on ties, on the colectivos from time to time.
overall, in the entire country, there are something like 440,000 latter day saints in argentina, but I still think the microcentro/san nicolas is not a very likely area for mass converts.
there is already neighborhood opposition to this temple- the barrio wants the land to become a park.
there is an article in the june 11 Clarin about this, you can read it here-
https://srsur.com.ar/real_estate/genera-polemica-el-primer-templo-mormon-en-la-city-portena/24872/
the property abuts a very old and historic convent, and there may be human remains as well as archeological value in the proposed site. historically there were 2 cemeteries there, and it has been green space for most of the time since the 1740s, with a relatively short lived undistinguished shopping there for a short time.
It will need the argentine equivalent of a special use permit- a specific exception to the prevailing zoning. This requires connections and money, most of the time, which, I would assume, the Mormons have, but it will no doubt be controversial, especially in the heart of the city.
The neighborhood is changing a lot, and there are more eyes on what is being built there than there used to be.
I actually have a friend who was the architect for the temple out by Ezieza, which is pretty suburban and fits the landscape- but this one is a very central urban spot. But that was in the mid 80s, and the political and civic climates towards big development were very different.
Interestingly enough, the probable architects for this one wont publicly admit it- which is kind of odd, as they are one of the biggest and most prestigious firms in town.
Me, I am against it. I think its an inappropriate use for a very central and important space- not many parcels that big come up in the central part of the city, and this rare occasion should be considered carefully.