As you can see in all the current screenshots been released, the Max Cap for 50 is 550,000 in the current version you can't gain EXP at 50 (thus displays as 0 in-game, in the dats it is 110k), so its assumed it will be like XI where you can EXP into the level and it stops at the cap. This would make the idea that the levelling curve has been increased by 500% (as its currently 100k to for 49-50).

In the recent live letter video where he was level 10, his cap was 10,690, where as currently it is 5,000 to go from 10-11. This would only be little over 200% increase. So the curve seems to be changing a lot. I dont think we have screenshots of levels outside 10 and 50. In the same video he kills a lv 6 mob (4 levels lower) and gains 45(+0) 46(+2%) exp, idk how that related to current but just a value. Mob same level gave 96exp. A synth he did gained him 570(+91%), botany I didnt get, sometimes he got exp, sometimes he didn't, sometimes he got two sets of exp, so have to wait =D

That said, he has mentioned in videos and even on that TGS Panel that levelling will be done primarily through questing, and even after hitting 50 you will have plenty left. Then there is also levelling dungeons, with the concept recently released being a 40-45 levelling area.

so all that, narrows down to, don't know how it will be XD