Used to be that a fractional upgrade was not a major upgrade although there have been exceptions with relatively generous feature additions. The next major upgrade would be 11 unless they skip a number, which happens sometimes, or they adopt a different naming convention. So (lostmemories) Apple has adopted a different upgrade plan since Logic 9 was released?
I would not group operating system upgrades with software upgrades. Seems like there is a separate evolution to consider where hardware plans are directly set in motion because Apple produces both its hardware and operating system. Seems.
In any case I will stick with 9 until 11 is released. 9 is good enough and Apple does not offer a grace period since they dropped the price and it is being sold through the App store. I know $199 is what many upgrades cost but paying $199 to get from 9 to 11 is more appealing than 9 to 10 only to have 11 come out within a couple of years (worse case scenario).