I'd agree with the idea that if it's not in March, it'll probably be next year-- but mostly because of the stuff that they're coming out with this year.
Hm, Shin Megami Tensei IV and Shin Megami Tensei X Fire Emblem, right?
The thing is that Hashino's said that the team devoted to Persona 5 is really only focusing on that, so if we don't see it this year I wouldn't say it's actually because of those other two titles in development at Atlus.
I guess I had begun to think that a 2013 reveal was inevitable, but now that I think about it there was no basis for that... To think that people have been wishing for a P5 reveal for each TGS beginning at 2009 and there's a possibility we won't even see it this year.
For fun, this is a pattern of interview dates where something "important" about Persona 5 was mentioned:
March 2010 - August 2011 - May 2012 - August 2012
17 months -> 9 months -> 3 months
I suppose the pattern would have suggested that it was being mentioned more and more, but it's been 6 months since the last mention.