To my knowledge, PR has long been succeeded by more sophisticated models. At one time, perhaps even now, Google had a team of mathematicians constantly tuning its ranking algorithm.
PR itself might be the foundation, but it definitely wouldn't be enough to build another Google scale system.
Links are still the single most important factor for ranking, though. I mean, there's a lot of other stuff going on, and the content/information extraction has advanced massively since the early days, but PR (or a similar concept) seems to still be the biggest part of determining how relevant a page is.
Atleast the future is not links. With the move towards reactive js based clients, restful api based services, links hardly have the requisite data for indexing. Even page content is extremely fickle to index.
Google must be having a js engine as part of its web indexing process.
They do, and have been using it for quite some time. Not only will they execute JS, they will also do AJAX requests and index the content that is returned.
Since the overwhelming majority of the web is still static, I believe links will be fine for the foreseeable future.
It's not a secret, they've never said that it changed.
Also, I do a lot of work for SEO/Affiliates. The exact same tech with pretty much the same content ranks top 2 for highly competitive keywords when hosted on a very high PR domain, and top 100-1000 when hosted on a normal, on-topic domain. This is consistent over multiple content areas, and it's why the large media companies have begun to sell/rent folders/subdomains on their site. Instant ranking (until somebody else buys access to a larger media company), no risk, as Google doesn't consider "paid publishing" as against their guidelines.
PR itself might be the foundation, but it definitely wouldn't be enough to build another Google scale system.