Slightly Live - Confused that you include Uprising in that closing paragraph, it's a pretty poor example both as a filler (as you outline thanks to delays) and a pretty poor story itself.
Uprising was trying to do one thing and that direct fill the gaps between the games. You would play Halo 2 to it's end, read the comic and be prepared for Halo 3.
And it failed. Regardless of it's quality, the publishing timeline went out the window was the original intention and since the story was supposed to be this preparatory direct tie, it fell apart.
Thankfully though, the story itself was largely inconsequential. The Kilo-Five Trilogy and the Forerunner Trilogy just seem much more substantial than Uprising. So I think there's more at risk for the reader in terms of being prepared and going through the events of both trilogies.
Uprising was never meant to be delayed the way it was but we don't know if Kilo-Five and Forerunner were or are on schedule - especially concerning considering how pushed back we know the Forerunner books have been.
In all, it's a minor worry. It's a small opinion piece just saying that not having both trilogies finish before Halo 4 just seems odd. (And as someone that eats books for breakfast, I'm always hungry!).
Uprising was something laser focused and directed and the smallest disruption ruined the entire point of it. The trilogies are less so focused, especially the Forerunner stuff s o hopefully in the end it won't matter much.