Rules for future node elections have not been released by dev team afaik. Best for the devs to work on the software and network stability now, let things settle down after the launch, then I'm sure details for future elections will be made public.
One thing for certain though, many more candidates will run next time, notary nodes are in the words of j777 'money printing machines' at a price just higher than where we are today

Forgive noobie question, but why you say 'money printing machines'?
Because they get to mine most of the new coins .....while the rest of the world gets to mine the left overs
Cheers Jon

So 64 notary nodes share majority of mining rewards between them, and non notaries can mine kmd but at a disadvantage.
So consensus is PoW like bitcoin, but the notaries work together and share block reward equally like a cartel.
And notary cartel membership is voted on by coin holders, preventing cartel from misbehaving.
A very interesting combination, not fully decentralized, but much more advantages from structure than other crypto coins.
Trust in the notary cartel will depend on election process, very interested to see more details when available.