Bonus rolls in 5.4
Warforged Seals will be obtained the same way as Mogu Runes were (weekly quest, exchanging for Lesser Charms). Cap of 10.
Mogu Runes will have a cap of 20 (up from 10, to bring them in line with Elder Charms)
Mogu Runes will be obtainable from the Timeless Isle:
"The Timeless Isle is inhabited by all manner of strange and powerful creatures that will test the mettle of solo explorers, but great rewards await the brave and skillful: epic loot, bind-to-account gear, Mogu Runes of Fate, pets, mounts, fun toys, and much more."
According to the comments above, you can buy them for 2500 Timeless Coins. More info at: http://ptr.wowhead.com/currency=777#comments
Of course, until 5.4 goes live, things could change.
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