SanDisk has started sending phone makers a Micro SDHC card that offers a whopping 12GB of capacity. Presumably it hopes the move will get the handset makers to start supporting memory cards that size. The Flash specialist's own list (PDF) of Micro SDHC handsets, for example, doesn't list a single phone capable of using the 12GB …
12 GB Micro SDHC card
Seeing that Windows Mobile 6 supports the SDHC technology, cards up to 32 GB in size, the HTC AT&T 8925 Tilt should be more than ready to accept them.
This should also hold true for the Motorola Q9, and any other Windows Mobile 6 phone on the market.