Even if we don't get Photoshop on the iPad in the near future, that doesn't mean that a simpler version of Photoshop won't appear for tablets or even phones. There are a ton of simple (for the user) operations available in Photoshop, that are memory-intensive, that could become viable on a tablet given more memory.

That said, the important point isn't Photoshop specifically. Consider the Surface Pro - despite its flaws, being able to run virtually any desktop app (decently) is huge. We are nearing that convergence point where the distinction between tablet and desktop becomes fuzzy. More memory and higher power, lower wattage CPUs are getting us closer.