Maybe, maybe not. I wouldn't say it's impossible, but I wouldn't bet on consoles being entirely replaced by PCs for a few reasons. First off, there's something to be said for a device which primarily (not only, judging by the web-browsing capabilities of most systems these days, but primarily) plays games. Some people prefer to keep their business and their pleasure separate--if you have a PC that has a lot of work or personal-related stuff on it, you may not want to put games on it, perhaps simply to avoid the temptation of playing when you're supposed to do work or whatnot. For those kinds of people, having a console which can only play games would be a way of allowing themselves to play games without being distracted when it really counts. It's a strange reasoning, but one I can imagine.
Secondly, it seems to me that consoles tend to have more longevity than computers. Maybe it's just me, but most computers I've had tend to last a year before getting bogged down with viruses and stuff. Again, you could chalk this up to my carelessness or stupidity (and I wouldn't argue) but my consoles (my PS2 in particular) have lasted for decades and are still operational. Consoles, it seems to me, are generally easier to operate and understand, which gives them an advantage that at least slightly makes up for their lack of versatility when compared to PCs.