And why would they add that in their report when they haven't even gave us the release date at a big event "like E3/TGS?" it wouldn't make any sense. Did they do that with FFXIII when the Fiscal year of 2010 report came out? ( FFXIII came out March 9th 2010, so it would be in that report with that logic.
We're risking veering off the base E3 discussion here by pushing towards release date stuff, but they indicated FF13 was targeted at launch within the 09/10 fiscal year in the 08/09 report that was released in March 2009, yes. The actual Western release date was announced eight months later. They also forecast shipping 26 million boxed units of games that year, which is key - most of those were projected to be FF13. Most of them were. 14/15 has less than half of that projected.
Anyway, yes - they're actually legally obligated to do these things. To not would be to actually break several stock market regulation rules, as such things could seriously effect stock prices. Given that company heads, such as Rogers, Matsuda and Wada all own shares, it'd be tantamount to insider trading, since they'd be holding on to stock thanks to knowledge other shareholders don't have. For instance, when Square's stock dropped in response to low estimates for FY 14/15, that was based off knowledge shared in the report, including a lack of information about FF15 and sales projections that indicate the game won't come before March 2015. If FF15 was actually coming, the fluctuating stock price would benefit those inside the company with shares - which includes many of the top flight staff - and that'd be illegal. If they know something is going to happen or come that could have a major effect, they have to share it. Sometimes they share it in a vague way - they might not say FF15, but they'd project a lot of units being sold that year. Nothing about this year's projection indicates any of SE's top-flight titles hitting shelves before March 2015 - not FF15, not a new Tomb Raider, etc.
They can of course keep longer-term secrets, because financial forecasts released to shareholders only look towards whatever the end of the next fiscal is. In theory, for instance, they can keep anything under development targeted at April 2015-March 2016 under wraps for a good while now, but on March 31st, 2015, they at least have to acknowledge that there's a mystery game they expect to sell (x) million copies of - even if they don't name the game until an E3 or PAX or TGS or whatever.
Insider trading carries a maximum sentence of 20 years in prison. So if they are hiding it for the element of surprise, well... er... I hope surprising the fans is worth it!
I don't think the fact that it'll never launch this fiscal has any real effect on the question of if it'll be at E3, mind...