According to Andriasang's translation of the rumor post, third parties have "a large number" of games ready for the launch window, to be distributed throughout February and March. But as for day-one, between Nintendo and third parties, it'll be about 10 games. Expect them all to come from the 15 playable titles at the Nintendo World event.
The site also claims that pricing for 3DS games will run around 1,000 yen ($12) more than the standard 4,800 ($57) yen DS game price, with more expensive games (your Square Enix stuff) running 2,000 yen higher. It's hard to tell how that will translate to American prices, considering the difference in base price between America and Japan.