OK so writing from experience now.
And to the OP, yes they're overhauling missions in 2.1, so yes that will absolutely affect the current 'methods' to rank up.
Current methods being: Stack 80 missions, and do them in one hit, rather than do each one individually for poultry rewards and progression.
What I would LOVE to see is 'Navy ascension mission arcs'. Maybe assassinate mr x, perhaps smuggle some weapons into station y, maybe transport x number of slaves to station xyz, assault a planet installation, maybe go mine aaaa material, and a finale would be to join a warzone and help out there for x number of kills / assists.
I don't know what to expect, but, all I know is that I spent a lot of time moaning on the forum about having to do mindless activities for a ship I really wanted. I have to admit a revelation, an epiphany hit me whilst laying in bed raging... and it struck me that they will make missions much much better in 2.1. Missions will be great, fun and everything pink with rose petals on top. I have faith in FD that they will pull some real gems out the hat.
BUT
The caveat that crawls along side this are fixes. Fixes that will nerf to hell the current methods of switching servers by logging off sessions, to 'refresh' the bulletin boards. They're overhauling the missions system, so only right to presume that this will be something in the targets to.
A week ago, I was unranked in Imperial Navy. Empire hated my ass. So, I work fundamentally incompatible hours for ED reputation grinding, I went about looking for ways to have both a life, and, get a Cutter. In the current system, it's possible. In the new system I highly doubt it. If you're going to grind rep, DO IT NOW. I'm Currently at Marquis, and 11% from Duke. Did I enjoy it? No, not at all. Would I ever do it again? No not at all. Was it fun? No not at all. Was it mandatory? Well, subjective. After 2.1 I guess it would be impossible for me to do it, as I have a life. Therefore if I was going to do it, it had to be now, and therefore was mandatory.
One thing I have learned in ED it's TAKE OPPORTUNITY whilst it exists. Sooner than later, the opportunity will be gone, and you'll see folks with 10,000,000,000 credit accounts, and think how the heck did they do it.. truth is, they put in no more effort than anyone else, all they did is just play the opportunities whilst they could, that's all.
I know folks in real life, that mortgaged their houses to invest in an opportunity arising from the earlier Russian oil gold rush.. He made several million, yet ED is the same.. See an opportunity to cash in, CASH IN. When it's gone it's gone. People only moan when they choose not to, or leave it too late, and then scream to nerf game mechanics that ultimately close the opportunity.
I'm waffling, you get my point. If you're gonna grind rep do it now. No idea how 2.1 will change things, but you betcha you wont be able to do it quite like this afterwards.
/Vx out
PS: I'll keep folks informed regarding my progress to duke later. Happy to share secrets (where's and how's once done), if folks are interested in that zero to duke week. Can easily be done quicker, but I only really had about an hour game time per night.