I would think that the SB have many projects going on at the same time - in various degrees of completion. When (and if) the SB figure out that the Shivan Groupmind is intentionally trying to kill them, things would definitely change. I'd expect that the SB would destroy any Groupmind ship that they come across, while at the same time putting a moratorium on any other race's development. Once the Groupmind was gone, the SB would have to figure out what to do about replacing it. Once the replacement was ready, the SB would again return to the development of other races.