Or it wouldn't because Apple would come up with a new way of doing the whole thing.
They could always shift undo levels and layers off to virtual memory. But god...that'd be terrible.
When it comes to certain things, there's no way you can get around the ram issue. By itself, freshly opened, I think Photoshop consumes about 80-200MB of ram. It's not much. Adobe could pop Photoshop as is onto an iPad now.
...but it'd hit a wall very, very quickly. See, there's a reason why PS ends up consuming upwards of 8GB of ram. When you start throwing in 20 levels of undo, adjustment layers, alpha masks, multiple high resolution images, all in a single .psd file. Work in CMYK, and you'll see your ram usage triple due to PS having to keep track of a much larger amount of data at a much finer level of detail.
Yeah, you could say they could make a way to compress layers you're not actively working on, but that'd only make the whole process of editing much, much slower and more cumbersome than it is now. The CPU would still have to uncompress the layer when you make it active, and compress the one you're leaving. But that'd spike CPU usage, and probably end up using more battery far more than having an extra couple GB of ram in there. That'd be a lot of effort on Adobe's part for what's ultimately a negative gain.
Sometimes you just need more ram.
Then again not that many folks, looking at the whole picture and not just the geeks on sites like this, really need 1024 levels of pressure sensitivity. A quarter of that would be more than enough for most users. A tenth that even.
What is really needed by almost all users are things like better display quality for outdoor use, better sensitivity for handwriting etc. If smaller sensitive points came with thousands of levels of pressure great, especially if it didn't greatly affect battery etc. If not, most would say ditch the tons of levels for now. Better to be able hand write clearly with only 120 levels or such.
Here's the way I see it. There are a ton, and I mean a TON of drawing apps and photo editors out for the iPad. For a surprising amount of people, it's a major reason why they use one in the first place. Even one of Apple's showcase apps, Paper, is dedicated to drawing.
You could argue that if people are using their iPads to draw now, why do they need more? Simple. Convenience. To emulate pressure, you have to fiddle around with tons of sliders and spend more time to get the same results you'd get just by pressing down a little harder on a Wacom digitizer.
Now Apple should always take battery usage into consideration, but I say if they're gonna do it, don't half ass it. They should go with
at least 512 levels of pressure. They should try to make it feel as natural and intuitive as possible while using a minimal amount of battery, but not sacrifice so much it's nearly useless.
And remember, Apple focuses on the majority so they would think that way as well.
The thing with the majority is that they'll use what they've got, and ignore what they don't. Like I know this older lady who has a Galaxy Note 2. She's hardly what I'd call a geek. Doesn't even have a computer at the house. But damn if she doesn't love that stylus. She's drawing pictures, writing notes, doing all kinds of stuff with it.
When I showed her my iPad, the first thing she did was pull out the stylus and attempt to write notes with it. Needless to say, she ended up being rather disappointed when it didn't work, and will probably never buy an iPad because of that.
So what does the majority want? Who knows? What seems like a useless feature to some, might be a killer feature to others. Having a bit of stylus support would, in my opinion, help Apple out far more than hurt them.