Bundled games retroactivity policy

Nope only after bundle date. Also most of the retroactive bundling comes from sales from cheaper regions.

No. There is a "bundled at ()" date that gets manually added for each game on the bundle list reflecting the day it was first available in a bundle/over 95% discount. If your GA was before that, it will keep its full value. (Though I am unclear on whether what matters is that it starts before that date or if it should end before the bundled date. Regardless, not likely to matter)

I mean, if today I GA a game that is not bundled but gets bundled a year from now, will I lose the rating then?

Nope. Retro-active bundling only goes back as far as the date the game first reached the "bundle-level" pricing. After that, your giveaway is only subject to the normal Steam price drops over time. :X

Great, thank you all very much

Ah, it's so good to see a question asked properly after reading the rules, and accepting the answer as well ^_^