No one here can answer the question "when or if....." in regards to the next version of Logic.. because if they knew they couldn't/wouldn't say anything anyhow because of the strict NDAs... So.. you can buy Logic 9 now and use it for a year or so and then upgrade... (You don't have to upgrade as soon as a new version is released and in fact, as many will confirm, I wouldn't recommend buying the next major version of Logic right away anyhow because it is bound to have bugs etc that need time to be properly ironed out) or wait and see and in the meantime, miss out on a really good DAW exprience.
That choice/gamble/whatever is yours to make....
There is now only one version of Logic... called Logic Pro... (Currently v9.1.8) which can only be purchased and downloaded from the Mac App Store. The Additional content mentioned below is downloaded from inside of Logic pro itself for free.
The previous versions were;
Logic Studio (The Boxed Set) of which there were two version 1.0 and later on 2.0 including Logic Pro 8 and Logic Pro 9 respectively
Along with that came DVDs containing the additional content (Instruments, Apple Loops known as Jam Packs, and other items... on a physical medium along with several other smaller programs such as Soundtrack Pro and Waveburner.. neither of which are available or supported by Apple now.
Logic Studio came as a Boxed edition bought online and them mailed to you, from Apple or via 'Bricks and Mortar' Stores
Logic Studio was discontinued when Logic Pro was made available on the Mac App Store. You might be able to locate one on Ebay for example... though frankly, for most people.. its better to stick with the latest download only version in reality.
Logic Express was a cut down version of Logic Pro and again, was only available on physical DVDs and is no lomger sold.
There were also older versions of Logic itself sold on a physical medium prior to Logic Studio being released.