Yes I went to 10K. There are a few late game quests that requires you to play past 5K (not because of the number of people but because the stories are long to unravel). I finished all the stories of v1.0.2 at about 8.5K.
I played for 3h until I had done all the stories (I think), including Project L.A.P.I.N., the videogame maker, the gold generating machine, curing chester, geordie sacrifice, trees protests, etc. I reached something like 10k people and 6k gold, but there is no more use to it sadly ;)
If there were more stories and the possibility to save progress, I would surely continue!
I disagree, Geordie has several strategies and at one point even offers to do good deeds ("angel") or even a cataclysmic sacrifice in exchange of a lot of money. If you accept this ritual, you will never see him again.
Also, to really progress, I had to select carefully my answers, if you always say "yes" you may not lose but your progress will be horribly slow.
/EDIT: I see that these posts are old so maybe the geordie character was extended in the latest release (1.0.2).
