A firmware update could theoretically improve card compatibility, but for the Nikon D90 there does not appear to be any firmware release that adds SDXC support for video recording. Based on the available information, no such update exists.

The “distortion control data” update is unrelated to memory-card support; it is lens correction data used to reduce distortion in compatible images.

So the practical answer is: if your D90 disables video with an SDXC card, you should assume the camera is not fully compatible with SDXC media, and updating firmware is unlikely to fix it. There’s also no established hack mentioned here that adds SDXC support.

Your best option is to use memory cards of the type and capacity the D90 officially supports, rather than relying on SDXC cards for movie recording.