It's a dilemma, indeed. Getting a cheapo body now to see how you like it is wise in itself, however, might become an expensive proposition if you want to change soon enough for the 6.
I know I personally miss the use of an EVF quite a bit, and didn't hesitate pre-ordering the 6 for many upgrades over the 5N. My motives are (you can always see if some of those resonate with you).
*Built-in EVF (paramount)
*Standard hotshoe to use my SB-600 (VERY important to me, I've been making do with the Sony dinky flash pretty well, but getting back the option of shooting in portrait orientation is going to be heavenly).
*Much better external controls (a real mode dial, and a couple of extra customizable buttons)
*Much improved user interface (I think they call it Quick Navi, and it's pretty similar to Oly's SCP). Noticeably there is a sort of "my menu" screen that calls back your five or six most used options. I've been missing that SORELY on the 5N.
*Built-in bounceable flash was very useful on the GX-1, and I expect it to work similarly on the 6.
*Better ergonomics, more grip, better coating. The 5N is a little soap bar of a camera, I'm not fond of its handling.
*Bottom hinged tilt screen. 5N has top hinged screen The stealth factor is very different. Top hinged screen (when tilted 90°) can be seen by the subject. Bottom is hidden from subject, so you can "shoot from the waist" unconspicuously. Good for street, shy people, etc.
*WIFI, pretty cool for direct download to phone and/or social network.
*Last but not least, better zoom lens, and HOPEFULLY usable AF, at last. IMHO AF on the 5N is barely usable (I've gotten more keepers focusing manually, ouch).
Those are my reasons to upgrade. Your mileage may totally vary. For me the 5 is a cracking fun camera as a manual focus nut's toy, but it's not viable as a primary, do-it-all camera. I'm hoping the 6 might be.