I also think that tablets will be around for a very very long time. It's like when you give someone gold that person will be very hesitant to give it back because they already got used to the good life. I love tablets and I love how simple they are to just take with me in my purse. Can't imagine my life without one at this point.
Surely laptops and tablets serve two different purposes? I have both and wouldn't be without either. I have a laptop that mostly sits on my desk. I am an academic and need something portable for when I do research in the field, but as most of my work is writing I don't require something overly powerful so don't need a desktop. At home, I use a mouse, keyboard and laptop stand for extra comfort. This is how I do any serious work. I also have a tablet which I use for general browsing around the house. I'm on the internet a lot, and the tablet is just more portable than a laptop. I sometimes do some work on it as well, mostly internet based research, like searching for articles, and taking notes. I don't want to do too much typing on it though. It's set up that everything important syncs from tablet to laptop. I like that my work is accessible at all times. I think tablets are ideal for people who just want to casually access the internet, while laptops are still more suitable for 'proper' typing work. For many of us, I do think the desktop has become obsolete. I accept that desktops are easier to adapt etc but not everyone needs those options, especially not at the price of portability. I guess I agree with other posters here that the future might be a hybrid type of laptop that can concert into a tablet. I've yet to personally try one of these myself but I might investigate that option for the future.
I don't think tablets will ever push laptops out of the market. There will always be people like me that will like to have an actual PC, instead of a tablet, in their hands.