[Renegade334]

Not a cliffhanger - there was no real sense of urgency in the epilogue. It was penned more like a bittersweet ending.

Spoiler:

- The world is at peace, but the next crisis could be brewing up behind the curtains.
- Power blocs (EA and PLANT) could be fragmenting due to intestine issues.
- Racial tensions are increasing with the Destiny Plan getting a new (albeit short-lived) lease on life, followed by an uptick in Blue Cosmos attacks.
- Kira and Lacus are together and could be closer than ever, but they are now emotionally wrung out - enough so that they need to bow out.
- Athrun and Cagalli vow to continue the fight even though it'll be a hard one and they're slightly at a loss as to how they'll do that without Kira and Lacus.
- Bottom line: peace has a cost, in the short and the long terms.

There are technically no loose ends after the movie, so, yes, if Bandai/Sunrise decide to rest on their laurels and let things stand as such, SEED Freedom could constitute the definitive end to the SEED saga. It does wrap up a few things, especially on the character relations side.

As for the afterword, no; Liu Goto mainly talks about the imagery driving some of his writing or being the backbone for certain scenes.
The only clue is that Fukuda (on his Twitter account? or it might have been in one of the post-movie interviews) said that he doesn't believe Kira and Lacus will ever "retire". That said, this reads as personal opinion, not an official response.

Spoiler:

For all we know, they could be living a quiet life in one of Rev. Malchio's properties (at least the ones that didn't get destroyed during the conflicts). It was mentioned that some of the orphans have grown up and might've moved elsewhere.

But that's all we're told. Officially, the two have been MIA since the battle on the Moon and the less the author says about them, the more poetic the ending feels...I believe. Less is more, so to speak.