There’s no official announcement yet about Diablo 3 Patch 1.0.8, but as Kojo noted in comments, Blizzard just switched both the PTR Feedback and PTR Bug Report forums to Read Only, so that no new posts or replies can be made. (No other D3 forums were given this treatment.) This isn’t absolute confirmation that the patch is coming during tonight’s maintenance period, but it seems the only logical explanation. (Yes, it’s an official soon™ warning.)
So… if you were dying for one last chance to run Act Three solely because it’s the only thing worth farming, hop online ASAP. You’ve got about 6 hours left as I type these words. If the weekly maintenance goes as planned, v1.08 should be live around 11am PDT, Tuesday morning.
Here’s the only official announcement, from a few days ago. If they update with something new, we’ll quote it for all to see.