There was a rumour going round that the 'trouble' network which just aired seasons 1-3 (that's were the set that's doing the rounds now came from), was due to air the remaining seasons. I recently sent them an email, asking when the remaining seasons will be shown, this was their reply:

Hi

Thanks for your e-mail,

Unfortunately at the moment we do not have the rights for the next series of "Hang Time". Please keep watching Trouble TV and check the Trouble website for more information.

Kind regards

Trouble

:(