This is all somewhat moot. Just like we call tissues Kleenex, and copiers Xerox machines, we'll likely call these devices whichever one becomes popular (I'd say Kindle is in the pole position right now) - which probably means we'll call them whatever Apple decides to name their device!
On a serious note, the problem with "liseuse" is that as an English speaker, I don't know immediately how to pronounce the word by sounding it out. I want to say "lis (as in list) - use" which just sounds weird. It simply doesn't roll off this English-speaker's tongue (nothing against French, but we are talking about finding a word for English speakers here).
As for a generic word, I think ebook and ereader are the most likely candidates. They are readily understood by just about anyone, and they simply explain what we're talking about. As for the eReader format - too bad. There simply is no better term to describe these devices.