There are a number of papers discussing the “extended bandwidth” of modern hearing aids. Most manufacturers use similar receivers (speakers) and most can make similar claims about what hearing aids can do under test settings. These settings and claims do not reflect the performance of the actual hearing aids in patient ears.
For instance, Aahz and Moore (2007) suggest that approximately 36 dB of insertion gain is required to provide audibility for a moderate hearing loss at 10,000 Hz.
Unfortunately, this is something that today’s hearing aids will not provide. In general, the odds of amplifying speech into the appropriate range beyond 7,000 Hz are very low.