Apple seem to have opening their doors a bit towards cryptocurrency applications in their App Store, since they just released a new update to their App Store Review Guidelines, where they write that "approved virtual currencies may be allowed as long as they don't break any laws".
“Apps may facilitate transmission of approved virtual currencies provided that they do so in compliance with all state and federal laws for the territories in which the app functions.” The clause in the "Purchasing and Currencies" section reads.
The legal status of Bitcoins differs from country to country, but is in general legal all across the world. While many jurisdictions have warned their citizens to be careful about Bitcoins and cryptocurrencies, they have not banned the usage of them. Apple did not confirm that Bitcoin applications will be available again and had no comments towards the new rules.
Apple removed all cryptocurrency related applications from their App Store earlier this year, receiving lots of negative publicity from the Bitcoin community, especially after removing the Blockchain application. Now it seems that Apple are willing to open up to virtual currencies once again, but maybe it is just to allow their own potential virtual currency, should they decide to create one, only time will tell.