Well no proofs whatsoever but plenty oh hints:
- Nami is the only one who gets to wear the hat which in OP is the thing with most symbolic mening (plenty of colour covers with nami wearing it too)
- there are afew times when they speak to eachother when you can tell they wouldnt speak the same way with anyone else
- plenty of hints throughout the story
- nami looks exteemely similar to aces mother
...
Plenty of hints, ppl always argue oda said no romance in OP, well romance for most ppl is lighting candles and spending the evening together or whatever (which in OP would just be plain awful) NOT showing them closer to one another and pairing them at the end (thats not romance, its justtelling how their lives turned out) ... Noone in their right mind would say DBZ was romantic ... Had pairings all the same. They also say luffy is too stupid for love, noone is to stupid for love, the only ones incapable of love ar psychos which luffy, who is actually off the scale passionate, just isnt. And there sthe Boa stuff ... Well it would beretty weird if the woman behind the Pirate King was abot 10 yrs older and almost twice his size, not to mention that luffy never showed any interest in her and the whole thing is more pf a gag.
So all in all at the end of the series it will probably happen but before that no, therell probably just be some more hints and maybe theyll get a bit closer