The only problem with the theory is that your assuming that they will either mass air, or surround themselves with useless defenses such as colonies or cannons. Though majority people go for the obvious strategys, such ass Carriers,Bcs, All-out defense for base, that would give you the tactical advantage.But some people, such as me, think outside the box, and use different ways to kill.
Like you use your scouts to suprise them, here is how i stand.
Zerg:Fully upgrade Hydras and Ling, send hydras in to rape defenses and units, while I send lings in to rape ground units and buildings. But,since they have fairly low hp, I decide to build massive d incase things dont work out.
Terran:I haven't though of any real strat with them. I mostly newb people with terran, by sending scvs^^
Protoss:Not to original, but send in corsairs to stop thier base d, then send in reavers,templars,archons, and dts.
This is just a basic strategy, sometimes Im forced to be like everybody else, and use the obvious strategys.
Gemini_Bloodian