I didn't see a samurai thread and I don't expect this one to be the main thread but maybe this will kick-start one with any discussion that gets brought up.
As you may or may not know, the actions for samurai were revealed:
Samurai Actions
I was looking through it all trying to figure out what a basic rotation would be and how it all fits together. I've made a couple assumptions in doing this:
1) All Hissatsu abilities (Kenki spenders) are OGCD.
2) The tooltip windows in the link have a GCD of 2.41 but I used 2.5
3) Potency calculations for Slash = pot*(1/.9) and DmgUp = pot*1.15
4) Hissatsu: Kaiten is a poorly written tooltip and should read "to 150%" rather than "by 150%"
5) Despite Midare Setsugekka having a cast time, it won't longer than the recast time to finish it and be able to cast your next GCD.
EDIT: reddit user /u/lenoan created a pretty nice spreadsheet to test out rotations. Linking it below this. To use it just create a copy for yourself from the file menu I believe. All credit to /u/lenoan
Spread sheet planner
Now, something else to consider if assumption '1' is true: Hissatsu Shinten and Kyuten both have a 1.0s recast time so I'm starting to think these are Kenki dump moves to spam if you are getting to much kenki but it also depends on the animation lock of these abilities.
A fun combo, which I listed in my spreadsheet as the last few moves is:
Hissatsu: Yaten (10- yalm disengage; empowers Enbi to 300 potency)
Enbi (20-yalm 300 potency ranged attack)
Hissatsu: Gyoten (Gap closer; gets you back into the action)
You have to have 10 Kenki to use it but it seems like it may be a natural addendum to the basic rotation.
The typical aoe rotation seems like it will utilize
Fuga -> Mangetsu (1 sen) -> Fuga -> Oka (2 sen) -> Iaijutsu (AOE version) and then stick in Hissatsu Guren when you reach 50 Kenki.
I believe the opener will probably utilize Meikyo Shisui since it will let you use your 3 combo enders back to back to stack your buffs up immediately. What direction you go from there is hard to say. You'll be at 30 kenki, with two spenders being 20 and 25 that do.
20 Kenki spender route:
If you use Kaiten (20 kenki; 150% WA) you would probably want to follow up with Midare Setsugekka (720 base potency), especially if you weaved in damage buffs like B4B. You'll be down to 10 kenki at this point so the question becomes is it more beneficial to build more kenki immediately or use the Yaten -> Enbi -> Gyoten combo?
25 Kenki spender route:
This just seems to be use Shinten and then be at 5 kenki. Probably not the best choice but at this point I'm not sure.
The third option becomes keep building kenki with a single target combo until 50 and then use Guren (800 potency is nothing to sneeze at even for single target).
Something to pay attention to is that since the duration of your debuff and buffs is 30s each, you have to reapply them roughly every 12 GCDs since I imagine keeping them up permanently is optimal.
One last thought I have for now is where does Higanbana (1 sen Iaijutsu; 240 potency + (35 potency * 20 ticks) = 940 potency attack) fit into it all?
I welcome any corrections and discussion to this thread. Please be civil, I am not the greatest theory crafter and am trying to spur forth conversation.
Useful Links and Theorycrafting:
A reddit users thoughts on linking kenki to potency and the importance of Hagakure
Daioh's indepth thoughts on potential Samurai openers
Probound turned Daioh's theory into a picture