Maybe, but considering the Note 3 hasn't gotten Marshmallow and may never get it, I'd say the chances are slim.
Pretty much this. Note 6 will hopefully release with N which will eventually trickle down to the 5 after an exclusivity period. The 4 released with Kitkat, got Lollipop and now getting Marshmallow (some of us at least, still waiting on the T-Mobile variant among others) so I kind of doubt that we will be lucky enough to get 3 full system updates.Of course not. They want you to buy a new phone!