My guess is that the snapshot date will be around the time of the PayPie pre-ICO to discourage people from finding it by selling their PPT. It'll force them to find liquidity somewhere else.
That's just a guess though.
PPT is going with big steps into a bright future, its smart to keep. Even if somebody helped a little bit.

Also it was known that Populous is active looking to extend there business modell if good chances come around(XBRL was already mentioned in there first whitepaper)
But I never expected how they would do that and how it would also be a gift to us investors and friends of Populous.
And again: "Populous Caribbean Tour 2018"
How I could imagine XBRL-Token works and some estimated number(just for fun - do not know what exactly will come)
Amount XBRL-Tokens : 60-120 Million (could imagine all tokens will be airdropped) *
Price for one XBRL-Report : 15 USD or 10 XBRL Token Extended XBRL-Report 30 USD or 20 x XBRL Token.
Access to XBRL-Report : Manual Web-Access for HTML automated over the blockchain from trading robots
XBRL-Token Life Circle :
PPT Investor got token over Airdrop and sell some to ED-Exchange
XBRL-User buys token on ED or direct at Populous Trading Robot buy over blockchain at ED or direct at Populous via trading API
Populous gets token and sells it at ED-Exchange or direct to customer / Burns from time to time token to increase value.
Price increase via : ToKen Burn, and rising demand for XBRL-Reports
Also rising revenue for Populous due to XBRL-Offering will have a positive effect on the PPT price itself
* What Popolus is doing here is a complete new ICO for XBRL-Token but for holders free of charge (and the business behind) if you hold PPT
They are worldwide the first again in this new business-sector !

THANK YOU, THANK YOU POPULOUS !