I'm not sure that changing a tag which is used 30 times in a region and is generally understood by editors in this region to a tag that is currently not at all in the OSM database is an improvement? And it doesn't seem like a shop=estate_agent to me, because it's for one development and the presentation is a considerable part.

If you really want, we could do something like office=residential_development_sales_centre which I think is less ambiguous. But honestly, we understand what shop=condo means and it's already in use. If you want to put "sales centre for a residential development: presentation and sales of apartments" into a wiki page for worldwide understanding, go for it.