The problem with mobile OS' is that the web browsers that come with them are a kind of "lite" version of their PC counterparts, e.g. earlier versions of iOS' web browser prohibited file uploads so if you wanted to post anything other than text on a forum, blog, etc., you needed an app.
Additionally, iOS prevents automatic playback of media (users have to click on a play button), making sequenced/synchronised multimedia presentations (a mainstay of elearning) impossible. We're constantly promised HTML5 replacements for sequenced multimedia but the truth is they just don't work on iOS browsers. Is this a deliberate policy and attempt to push more agencies and developers into distribute apps on iTunes? That's anyone's guess.
I reckon mobile devices will get much better given enough time (a few years?). Perhaps Intel will eventually come out with some reasonably priced mobile "beefy" CPUs? Until then, mobile devices will be too limited for many of the demands that elearning makes of them and developers will be pushed to find workarounds such as replacing browser activities with apps and reducing the functionality of activities made for mobile browsers.
I waited until 2005 to get a laptop; the year in which entry level laptops became "useful." Let's see how long it takes for them to make "useful" mobile devices, e.g. have decent file management, can access everything on the web without the need for apps/conversion, etc.