It would be interesting to have something akin to Invasion as a game type in BTB, yeah. I think game types that work through phases have a lot of potential to be fun, but the execution of Invasion was poor.
The exact wording in the Bulletin:
Q: We already know Elites are not in, which means no Invasion as we know it in Halo 4. Have you considered releasing a game type (both at launch and after launch) which relied on some of the aspects which made Invasion great? -Gabotron ES
A: Elites are in Campaign. Elites are not playable MP types. We will, however, add some interesting variety to MP which will scratch that itch.
I'm still not sure if he was talking about scratching the Invasion itch (the question) or the playing-as-Elites itch, which the answer focused on.