It's worth noting that they're launching on Epic Games, free for two weeks, tomorrow, I believe. So this is an update they were just recently effectively paid to do. Though of course, it also benefits the folks on Steam as well.
Will it benefit the folks on Steam? I was under the impression the update was not coming to Steam for a year, although the end of the blog post does seem to suggest it'll be coming out. Maybe unclear reporting when the patch was announced a few weeks ago?
My reading of the blog post would be yes - "We’re slowly updating the game everywhere it’s currently available over the course of this and next week." - but I wouldn't take it as a definitive statement.
The post says they're updating it on every platform it's published on. The "Secret World of Goo Download Location" already has the 1.5 built, if it hasn't rolled out to steam I expect it'll come soon.
