I cant say anything about the intentions of Brehon or any other Q leader but since karma we have seen frequently alliances being rolled twice (on purpose). It happened to Pacifica, to Polar, to XX.
It wouldnt surprise me if the same happens with DH.
PS. Assuming that DH will loose or get a "white peace", which is only a possibility.
ADDED: I think Brehon is right, while Umbrella is certainly very good at nation building (some credit to Roq by the way) this excellence was facilitated by pollitics, which by the way is also a very important (if not the MOST important) in an alliance.