Yet a new and also a final version of the roman in the 4 weights is coming. This version takes advantage of the last 6 months of research and experience testing rendering in the large group Google web fonts that Sorkin Type Co. has released into service.* In addition to better rendering this version will be prettier and more consistent in its construction.
Perhaps the best things about it will be the addition of glyph coverage for a far broader range of languages including Czech, Hungarian, Maltese, Polish, Romanian, Slovak, Turkish, Western Apache (Diné bizaad), Welsh, and many others.
In addition, this version will also cover non-letter glyphs that are present in the Mac Roman encoding, ISO 8859 or Latin 1, and Windows ANSI. It seems unlikely that anyone will make much use of these but this will make Merriweather complete.
Because this version will be final it will be also (finally) be hinted for Windows in VTT.
*These include: Hammersmith, Pompiere, Black Ops, Voltaire, Short Stack, Fjord, Contrail, Spinnaker, Ovo, Limelight, Pinyon Script, Supermercado One, Vast+Shadow, Gravitas, Passero, Atomic Age, Asset and Goblin.