If i remember right,reaching six paths sannin simply means that you don't get the minimum season rewards
but after reaching six p, your ranking-at the start of a new season-will become special jonin and if you do not change it you will recive special jonin rewards,if you manage to make your special jonin into a say super kage,you will recive super kage reward,not sure if the whole reset at the start of a new season thing applies to ranks other than six p though

if you get six paths you will get full rewards for whatever ranks you are afterwards,if you do not,you will only get minimal rewards

p.s random rant:
i half suspect them doing this to just take some programming load of their backs (maybe to transition ones arena into the"new"system so to speak rather than it having anything to with the game play)also if one was to take advantage of the strongest players getting back so special jonin every season i think they could reach six paths without actually facing those guys in 2 or 3 months(not sure though)

I'm currently facing the same problem,being stuck at anbu and not being able to go any higher simply because no one is there to fight
if they manage to fix that problem somehow it will become a system superior to the last one
p.s
does anyone know how the cross server thing works and if it has been implemented in every server or not?