4e is 9 months away. And no one can stop you from continuing your 3.5 campaign indefinitely. You still own the books right? I know people still playing 1ed AD&D! They never bothered with 2e or 3e. So why should you worry about 4e?
Back in the 80s, yes 80s, when I started playing D&D (with the blue-box, then Red Basic Set) the world of RPGs was fresh. Everyone one was coming out with new and different RPGs. Traveller, Role Master, Palladium, Champions, etc. Their rules were completely different, and no one worried. No one was bothered, we tried every game we could afford on our elementary school or middle school allowances. It was fun testing out and making characters for these new games, and deciding who was going to be "DM". There were no "conversion guides" to take our characters from Basic D&D to AD&D. We just made new ones, or did our best to re-interpret our "Elves" into Elven Fighter-Magic User-Thieves.
The only thing I'm personally upset about is losing Dungeon and Dragon magazines. I still have a bunch of my old issues for the 80s, and all the issues relating to D20 and 3.0 & 3.5. And I prefer professionally printed & bound products vs. laser printed PDFs.
And as I've said somewhere else (Enworld or Wizards), D&D 4e is NOT competing with MMO games. D&D Insider is not turning D&D into a MMORPG! D&D Insider is Subscription Based Supplementary Tools & Materials. There has always been, and will always be Free or low cost 3rd party alternatives to D&D Insider. It has also be said that the FAQ and Errata will be available FOR FREE.
So quit getting your loin cloths into a bunch, and let it unfold. I can guarantee that you will NOT be able to stop WOTC from producing D&D 4e the way they are going to to produce it. And if you don't like 4e, you will go and play something else, such as 3.5e, True20, or CoC, or Exalted, or Role Master, or AD&D 1st.
Paizo will also continue to produce quality products for great games. Whether it's 3.5, 4e, True20, C&C or their own IP. You can count on that.
Game On!