Conclusions aren't always so foregone - a lot can happen in the time it takes a five-city empire to research all the space techs. Especially if it goes to nukes, which can really mess up the top-city list.
That said, I'm certainly aware of the drudgery of playing out a foregone conclusion. I would say this - you can take the scoring for completed items, which would be the the culture and for honorable play in completed ages, but not for anything incomplete which would be the other bonuses of victory, top-cities, and modern/full-game honorable play.
Sound fair? (And if Sirian has any comments or ruling, please weigh in of course.)
I hope you'll provide us some interesting reports from the Conquests beta (they didn't NDA you, did they?)