Of course higher-level techs will be more expensive -- they say as much in the interview -- but that is not enough to keep players from skipping intermediate technologies and going right to the end. It would be a terrible system.Not saying it will (or should) be this way, but they could make it work by having the cost be higher the further from the main thrust of your research you stray.
Having watched the PAX panel, it seems that the way the tech web works is that there are indeed prerequisites: you can only research techs that are adjacent to what you've already researched. You can move outward to the next tier, or laterally within the same tier, but either way that's still a prerequisite, it's simply not a "fixed" prerequisite.