I can't remember the last update I read on it, I just remember I haven't seen any articles titled "At Last! The F-35's Super Visibility Helmet Is Fully Operational!" yet. Ambitious technology, and the fighter's not 'crippled' by any means with its current capability, but eventually I hope they get the last bugs fixed.
This article implies a significant change beginning with lot 15 birds this year.

F-35′s X-Ray Vision System Is Getting An Upgrade, But Will It Actually Save Money?
Lockheed Martin and Raytheon say the update will improve the jet's capability and save money, but it could exacerbate existing sustainment issues.

The contract announcement is too vague to verify if the DAS upgrade made it as part of TR4.

Pentagon and Lockheed Martin Finalize Lot 15-17 Agreement, Capping a Year of International Growth
/PRNewswire/ -- The F-35 Joint Program Office and Lockheed Martin have finalized the contract for the production and delivery for up to 398 F-35s for $30...
