"I for one share an immense dislike of "Human inferiority/limitation" philosophies, but these books didn't offer one (no Trek does, in my view) and there's nothing wrong with asking others for help when you need it."
Weren't you applauding Sci's speech about human imperfection, human limitation and human failure, depicted in "Destiny", opposed to the Caeliar's superiority - beings who easily solved a problem that was way beyond humanity's capabilities?
, Deranged Nasat
OK. Let's run some numbers. Initially, there were 7000+ cubes. 3500/half were destroyed in Dax's plan. A few thousand more were destroyed by transphasics.
Let's say 1500 remain. Let's say Picard manages to gather the majority of those cubes in one place - by sending fake omega particle readings or some other smart (for a change) plan - and destroys them with the thalaron weapon.
Starfleet has slipstream drive - when it comes to crossing intergalactic distances, it's the only way to fly, baby!. In 100 years, thousands/tens of thousands of convoys will be send beyond the milky way - carrying tens of BILLIONS of refugees. The alpha/beta civilizations will survive.
"Space is big. Really big. You just won't believe how vastly hugely mindbogglingly big it is." - That goes double for intergalactic distances. The borg can have as many cubes as they want. They will never find all the convoys. Not even close.
We know many species ascend into beings made of pure thought, pure energy - incredibly powerfull beings. Sooner or later, humanity or another alpha/beta species will manage this performance. It may take eons, but then, the tide of the war will turn in humanity's favour.
And, unlike the Federation, the borg are not the creative type; they don't develop technologies, they assimilate them. I think that, after 50-100 years, the Federation will be in a much better position to confront the borg.