...we all remember the Sony Walkman and the Atari 2600.. Hell - many fondly remember (me included) their Sinclair Spectrums with it's rubber keyboard, their very first computer; I think I could even still smash out a few lines of BASIC. The very first of their kind.
I think the iPad will be remembered as the first of it's kind - while technically not correct, the fact is that the iPad is the first successful consumer tablet computer; wether it's detractors like it or not.
Given the amount of vapourwear tablets being touted and the "train crash" that is the HP tablet running windows 7's (video on endgadget if you want to feel terribly uncomfortable on HP and Microsofts behalf - it's so painful to watch it's not even funny), I think the iPad will remain the dominant tablet device for the foreseeable future.
Actually, given how poorly many companies have risen to the iPad challenge so far, I wouldn't be surprised if they delay the release of the 2nd generation for a few more months, just to take full advantage of any 'improvements' they have in the pipeline. Keep those competitors chasing
*I lie. It's EXTREMELY funny. Especially given the apple haters saying how they're going to have a $400 tablet running Photoshop.. Ha.. That thing can't even run IE smoothly. "look how I scroll this page" (nothing on the screen moves). It's looks like he's permanently using teamviewer... Actually - scrub that - team viewer is smoother than that on my iPad... over the Internet.