My prediction is that the MacBook Air will eventually be discontinued, and the MacBook/MacBook Pro will drop the internal optical drive and become thinner and lighter. It won't be as thin and light as a MacBook Air, but it will be a more powerful machine. In other words, it will be a hybrid of the current MacBook Pro and the MacBook Air.
This is pure speculation on my part. I have no insider information about this. It's just an educated guess.
As long as I'm guessing, I expect this redesign will happen in fall 2010. This is the typical timeframe for a notebook refresh, and it will be close to the time that Intel will put the Core 2 Duo on end-of-life.
I just have to disagree. Apple is a mobility electronics company. I believe an MBA is powerful enough for just about any MB user. Therefore, why would Apple EOL the most mobile Mac that actually runs OS X? It just doesn't make sense. Apple could go a few different directions, but I see the iPad and iPhone as selling more MBAs and less MBs. People want to be extremely mobile, and many people want OS X. Apple is going to sell more and more Macs just by selling more iPads and iPhones.
If Apple just upgrades the MBA to 4 GB RAM and a 180 GB HDD in the low-end version, Apple could sell a ton of them. If Apple actually makes a high-end version with an Arrandale CPU and discrete GPU, as rumored, I believe Apple could sell MBAs to would be MBP buyers. There is a gigantic price range potential in the MBAs. People that are new to Apple's Macs, which as many as 50% of in-store customers are, will see more value in portability.
I feel like there's more room for more MBAs, more options on those MBAs, and multiple potential strategies. Sure, the MB/MBP will get thinner without optical drives, but some users want 10-hour batteries which don't happen in ultraportables without killing the GPU. Whenever Apple uses the MBA "styling" on the MB/MBP, it will further "Airize" the MBA. There's always more room for a more ultraportable Mac that runs OS X.
I believe Apple is equally abandoning innovation on all Macs and OS X users across the board in the short-term. Apple only upgraded the MBP after eleven months because sales were slipping on that model. We can all tell that reading forum threads. Apple is still selling more Macs year over year, because it updates one Mac to encourage sales. The iMac updates late last year were substantial, and I am certain that and consistent MB sales kept numbers high. Apple left the MBA and Mac Pro unchanged because it simply hasn't had the time with the iOS products and focus on software. It is a cycle. Apple isn't going to stop making Macs and the end of the Macs are nowhere in sight. Apple might sell more iPads and more iPhones, and over half its revenues might be iProducts... but half its net income is still from Macs. Bottom line, Apple makes a heck of a lot more money selling a MacBook Pro than selling an iPod Touch or iPad.
Apple absolutely must focus on iOS products as they're rapidly growing markets with new users selecting iPhone over the competition. Same thing with the iPad. Once these markets stop growing so rapidly, Apple will tend to focus on each more equally. Right now it makes business sense for Apple to try to grow the iProduct markets and capture as much market share as possible. It is incredibly more difficult to get an Android/Windows 7/Blackberry user to switch to an iPhone than to just get the users to select the iPhone with their first smartphone purchase. Same goes for iPad over other tablet devices which are all failing miserably to date.
It sucks being a Mac user right now. But in the long-run, Mac users will get their products back in the spotlight. For now, Apple can grow the Mac sales just by selling more iProducts and getting those users used to the "Apple Ways." Apple will not abandon the Mac users, so everyone needs to calm down and get these bogus dark fantasies/nightmares out of their heads. When I look at it from a business standpoint, Apple is absolutely doing the right thing. As a Mac user, the right thing isn't very fun right now... but Mac users will have their day again. I believe Apple will make big changes to Macs in the next 18 months. Apple has some great iProducts that can really compete well and absorb new-to-market users over the next year. I suspect not just new great MBPs, but also new great MBAs and other Macs too. Something innovative and incredible is definitely in the works for Macs, and I suspect all of the "End of Days" stories about Macs will disappear. A little over a year ago the iMac was really old and outdated, and Apple gave it a marginal update in Early 2009. Well it was basically a "bump." In Late 2009, Apple gave the iMac the "real" update... and the 27" iMac was stunning. I suspect the same scenario with the next MBP updates... and MBAs thereafter.
One last bit of hope. Apple has successfully implemented every "option" people have expected in iPhones since the beginning. The forward-facing camera is there. The LED-flash is there for a much nicer camera. The retina display is amazing. The design is incredible. The battery life is better. This is an iPhone that has been innovated tremendously and doesn't have much more possibilities in the next year. There's nothing people want now that the iPhone doesn't have. People on Android forums are wanting the forward-facing cameras and gyroscopes in their Android smartphones now. Apple has the successful phone design with all of the parts buyers want. Apple may only have a tiny update next year. If we think about it, the iPhone has what everyone wanted. Apple will be able to triple current sales with this exact iPhone once it gets it on Verizon. There's talk of T-Mobile and Sprint too. Apple will not need to add or update anything to sell on these other networks. Verizon's 4G is potentially (rumored) going to be introduced later this year with a new iPhone. That means Apple is already done all of the work for extreme innovation on the iPhone for probably the next year at least. Apple will focus some time on the next iPad version, but it's going to have a lot of time to re-focus its resources on OS X 10.7 and the entire Mac lineup... I believe us Mac users will see big rewards in our long waits. I feel like MBA users, MBP users, and all of the other Mac users will see some big Mac news over the next twelve to eighteen months.