You're not being paranoid. Inception is going to get past $200 million domestically, do as well or better internationally, fare fantastically on home video, and rack up all sorts of end-of-the-year awards, very possibly including Oscar nods for Best Picture and Best Director, not only for itself but as a way for the Academy to atone for stiffing The Dark Knight. If you don't think Warner Brothers isn't slavering for a sequel, you're nuts.
But an Inception sequel will be harder to pull off than it looks. For one thing, name a sequel starring Leonardo DiCaprio. The correct answer: Critters 3. But that was when he was 17 and still doing TV. Since then, there's not a single sequel on his résumé, which is sort of amazing when you think about it.