If you are a Paradox fan you will recall that many of their previous game featured an end, which most of the time was abrupt (even if you knew the ending date). I pray that they add an option ingame (menu or otherwise) that allows you to continue even after the official end date - previous versions of their games have always relied on user made/hacked exe's and patches to accomplish this when paradox themselves could have whipped up an offical one in less that a day. I understand that there will be certain limitations due to the game structure and AI (i.e. no more tech trees to explore, no more historical events occuring, etc...) but sometimes we just want a few more years to reek havoc on the world.
I've always hated time limits. I stopped playing EU3 for exactly that reason, and didn't start playing again until I realized the game files could be screwed with so you could change the 500 year game in 50000 years. And that was only possible with In Nomine, the previous versions had to be hacked.
I had hoped that they would have at least extended the time limit from HOI2 to HOI3. Since they haven't, however, I would imagine that they will release expansions later on. I don't like this tactic, but it will give us all a chance to take our empires and regimes into the next decade or two. I just hope they don't wait a terribly long time to release them.